Add Iterate Over A Dictionary as a Python TIL

README.md

@@ -10,7 +10,7 @@ working across different projects via [VisualMode](https://www.visualmode.dev/).
 
 For a steady stream of TILs, [sign up for my newsletter](https://visualmode.kit.com/newsletter).
 
-_1726 TILs and counting..._
+_1751 TILs and counting..._
 
 See some of the other learning resources I work on:
 
@@ -29,6 +29,7 @@ If you've learned something here, support my efforts writing daily TILs by
 * [Ansible](#ansible)
 * [Astro](#astro)
 * [AWS](#aws)
+* [Bash](#bash)
 * [Brew](#brew)
 * [Chrome](#chrome)
 * [Claude Code](#claude-code)
@@ -126,6 +127,10 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Turn Off Output Pager For A Command](aws/turn-off-output-pager-for-a-command.md)
 - [Use Specific AWS Profile With CLI](aws/use-specific-aws-profile-with-cli.md)
 
+### Bash
+
+- [Edit The Current Command Prompt](bash/edit-the-current-command-prompt.md)
+
 ### Brew
 
 - [Clean Up Your Brew Installations](brew/clean-up-your-brew-installations.md)
@@ -241,6 +246,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Reload The nginx Configuration](devops/reload-the-nginx-configuration.md)
 - [Resolve The Public IP Of A URL](devops/resolve-the-public-ip-of-a-url.md)
 - [Running Out Of inode Space](devops/running-out-of-inode-space.md)
+- [Set, Get, And Unset Env Vars With Dokku](devops/set-get-and-unset-env-vars-with-dokku.md)
 - [Set Up Domain For Hatchbox Rails App](devops/set-up-domain-for-hatchbox-rails-app.md)
 - [SSH Into A Docker Container](devops/ssh-into-a-docker-container.md)
 - [SSL Certificates Can Cover Multiple Domains](devops/ssl-certificates-can-cover-multiple-domains.md)
@@ -720,6 +726,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Capture Screenshot To Clipboard From CLI](mac/capture-screenshot-to-clipboard-from-cli.md)
 - [Check Network Quality Stats From The Command Line](mac/check-network-quality-stats-from-the-command-line.md)
 - [Clean Up Old Homebrew Files](mac/clean-up-old-homebrew-files.md)
+- [Control Which Monitor App Switcher Appears On](mac/control-which-monitor-app-switcher-appears-on.md)
 - [Convert An HEIC Image File To JPG](mac/convert-an-heic-image-file-to-jpg.md)
 - [Default Screenshot Location](mac/default-screenshot-location.md)
 - [Detect How Long A User Has Been Idle](mac/detect-how-long-a-user-has-been-idle.md)
@@ -754,9 +761,11 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Create Umbrella Task For All Test Tasks](mise/create-umbrella-task-for-all-test-tasks.md)
 - [List The Files Being Loaded By Mise](mise/list-the-files-being-loaded-by-mise.md)
 - [Look In Ruby Version Dotfile](mise/look-in-ruby-version-dotfile.md)
+- [Override Your Project Mise File](mise/override-your-project-mise-file.md)
 - [Preserve Color Output For Task Command](mise/preserve-color-output-for-task-command.md)
 - [Read Existing Dot Env File Into Env Vars](mise/read-existing-dot-env-file-into-env-vars.md)
 - [Run A Command With Specific Tool Version](mise/run-a-command-with-specific-tool-version.md)
+- [Search Through Bin Paths For Tool Locations](mise/search-through-bin-paths-for-tool-locations.md)
 
 ### MongoDB
 
@@ -862,6 +871,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Clear The Screen In psql](postgres/clear-the-screen-in-psql.md)
 - [Clear The Screen In psql (2)](postgres/clear-the-screen-in-psql-2.md)
 - [Compute Hashes With pgcrypto](postgres/compute-hashes-with-pgcrypto.md)
+- [Compute Median Instead Of Average](postgres/compute-median-instead-of-average.md)
 - [Compute The Levenshtein Distance Of Two Strings](postgres/compute-the-levenshtein-distance-of-two-strings.md)
 - [Compute The md5 Hash Of A String](postgres/compute-the-md5-hash-of-a-string.md)
 - [Concatenate Strings With A Separator](postgres/concatenate-strings-with-a-separator.md)
@@ -1029,9 +1039,17 @@ If you've learned something here, support my efforts writing daily TILs by
 ### Python
 
 - [Access Instance Variables](python/access-instance-variables.md)
+- [Access Most Recent Return Value In REPL](python/access-most-recent-return-value-in-repl.md)
 - [Break Debugger On First Line Of Program](python/break-debugger-on-first-line-of-program.md)
+- [Check If Package Is Installed With Pip](python/check-if-package-is-installed-with-pip.md)
 - [Create A Dummy DataFrame In Pandas](python/create-a-dummy-dataframe-in-pandas.md)
 - [Dunder Methods](python/dunder-methods.md)
+- [Easy Key-Value Aggregates With defaultdict](python/easy-key-value-aggregates-with-defaultdict.md)
+- [Install With PIP For Specific Interpreter](python/install-with-pip-for-specific-interpreter.md)
+- [Iterate First N Items From Enumerable](python/iterate-first-n-items-from-enumerable.md)
+- [Iterate Over A Dictionary](python/iterate-over-a-dictionary.md)
+- [Keep A Tally With collections.Counter](python/keep-a-tally-with-collections-counter.md)
+- [Load A File Into The Python REPL](python/load-a-file-into-the-python-repl.md)
 - [Override The Boolean Context Of A Class](python/override-the-boolean-context-of-a-class.md)
 - [Store And Access Immutable Data In A Tuple](python/store-and-access-immutable-data-in-a-tuple.md)
 - [Test A Function With Pytest](python/test-a-function-with-pytest.md)
@@ -1070,9 +1088,12 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Cast Common Boolean-Like Values To Booleans](rails/cast-common-boolean-like-values-to-booleans.md)
 - [Change The Nullability Of A Column](rails/change-the-nullability-of-a-column.md)
 - [Change The Time Zone Offset Of A DateTime Object](rails/change-the-time-zone-offset-of-a-datetime-object.md)
+- [Check How Database Is Configured](rails/check-how-database-is-configured.md)
 - [Check If ActiveRecord Update Fails](rails/check-if-activerecord-update-fails.md)
 - [Check If Any Records Have A Null Value](rails/check-if-any-records-have-a-null-value.md)
 - [Check Specific Attributes On ActiveRecord Array](rails/check-specific-attributes-on-activerecord-array.md)
+- [Check The Current Named Log Level](rails/check-the-current-named-log-level.md)
+- [Clean Up Memory Hungry Rails Console Processes](rails/clean-up-memory-hungry-rails-console-processes.md)
 - [Code Statistics For An Application](rails/code-statistics-for-an-application.md)
 - [Columns With Default Values Are Nil On Create](rails/columns-with-default-values-are-nil-on-create.md)
 - [Comparing DateTimes Down To Second Precision](rails/comparing-datetimes-down-to-second-precision.md)
@@ -1426,6 +1447,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Limit Split](ruby/limit-split.md)
 - [List The Running Ruby Version](ruby/list-the-running-ruby-version.md)
 - [Listing Local Variables](ruby/listing-local-variables.md)
+- [Make A Long String Of Text Readable](ruby/make-a-long-string-of-text-readable.md)
 - [Make An Executable Ruby Script](ruby/make-an-executable-ruby-script.md)
 - [Make Structs Easier To Use With Keyword Initialization](ruby/make-structs-easier-to-use-with-keyword-initialization.md)
 - [Map With Index Over An Array](ruby/map-with-index-over-an-array.md)
@@ -1479,6 +1501,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Single And Double Quoted String Notation](ruby/single-and-double-quoted-string-notation.md)
 - [Skip Specific CVEs When Auditing Your Bundle](ruby/skip-specific-cves-when-auditing-your-bundle.md)
 - [Skip The Front Of An Array With Drop](ruby/skip-the-front-of-an-array-with-drop.md)
+- [Specify Default For Data Definition](ruby/specify-default-for-data-definition.md)
 - [Specify Dependencies For A Rake Task](ruby/specify-dependencies-for-a-rake-task.md)
 - [Specify How Random Array#sample Is](ruby/specify-how-random-array-sample-is.md)
 - [Split A Float Into Its Integer And Decimal](ruby/split-a-float-into-its-integer-and-decimal.md)
@@ -1566,6 +1589,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Kill Other Connections To A Session](tmux/kill-other-connections-to-a-session.md)
 - [Kill The Current Session](tmux/kill-the-current-session.md)
 - [List All Key Bindings](tmux/list-all-key-bindings.md)
+- [List Processes Running Across All Session](tmux/list-processes-running-across-all-sessions.md)
 - [List Sessions](tmux/list-sessions.md)
 - [Open New Splits To The Current Directory](tmux/open-new-splits-to-the-current-directory.md)
 - [Open New Window With A Specific Directory](tmux/open-new-window-with-a-specific-directory.md)
@@ -1625,6 +1649,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Check The Current Working Directory](unix/check-the-current-working-directory.md)
 - [Check The Installed OpenSSL Version](unix/check-the-installed-openssl-version.md)
 - [Clear The Screen](unix/clear-the-screen.md)
+- [Combine All My TILs Into A Single File](unix/combine-all-my-tils-into-a-single-file.md)
 - [Command Line Length Limitations](unix/command-line-length-limitations.md)
 - [Compare Two Variables In A Bash Script](unix/compare-two-variables-in-a-bash-script.md)
 - [Configure cd To Behave Like pushd In Zsh](unix/configure-cd-to-behave-like-pushd-in-zsh.md)
@@ -1673,6 +1698,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Fix Previous Command With fc](unix/fix-previous-command-with-fc.md)
 - [Fix Shim Path After asdf Upgrade](unix/fix-shim-path-after-asdf-upgrade.md)
 - [Fix Unlinked Node Binaries With asdf](unix/fix-unlinked-node-binaries-with-asdf.md)
+- [Format And Display Small Amounts Of Columnar Data](unix/format-and-display-small-amounts-of-columnar-data.md)
 - [Forward Multiple Ports Over SSH](unix/forward-multiple-ports-over-ssh.md)
 - [Generate A SAML Key And Certificate Pair](unix/generate-a-saml-key-and-certificate-pair.md)
 - [Generate A Sequence Of Numbered Items](unix/generate-a-sequence-of-numbered-items.md)
@@ -1695,6 +1721,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Ignore A Directory During ripgrep Search](unix/ignore-a-directory-during-ripgrep-search.md)
 - [Ignore The Alias When Running A Command](unix/ignore-the-alias-when-running-a-command.md)
 - [Include Ignore Files In Ripgrep Search](unix/include-ignore-files-in-ripgrep-search.md)
+- [Inspect EXIF Data For An Image File](unix/inspect-exif-data-for-an-image-file.md)
 - [Interactively Browse Available Node Versions](unix/interactively-browse-availabile-node-versions.md)
 - [Interactively Switch asdf Package Versions](unix/interactively-switch-asdf-package-versions.md)
 - [Interpret Cron Schedule From The CLI](unix/interpret-cron-schedule-from-the-cli.md)
@@ -1756,6 +1783,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Show A File Preview When Searching With FZF](unix/show-a-file-preview-when-searching-with-fzf.md)
 - [Show Disk Usage For The Current Directory](unix/show-disk-usage-for-the-current-directory.md)
 - [Show The Size Of Everything In A Directory](unix/show-the-size-of-everything-in-a-directory.md)
+- [Show Tree View Of Processes And Subprocesses](unix/show-tree-view-of-processes-and-subprocesses.md)
 - [Skip Paging If Output Fits On Screen With Less](unix/skip-paging-if-output-fits-on-screen-with-less.md)
 - [SSH Escape Sequences](unix/ssh-escape-sequences.md)
 - [SSH With Port Forwarding](unix/ssh-with-port-forwarding.md)
@@ -1771,6 +1799,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Unrestrict Where ripgrep Searches](unix/unrestrict-where-ripgrep-searches.md)
 - [Update Package Versions Known By asdf Plugin](unix/update-package-versions-known-by-asdf-plugin.md)
 - [Use fzf To Change Directories](unix/use-fzf-to-change-directories.md)
+- [Use Negative Lookbehind Matching With ripgrep](unix/use-negative-lookbehind-matching-with-ripgrep.md)
 - [Use Regex Pattern Matching With Grep](unix/use-regex-pattern-matching-with-grep.md)
 - [View A Web Page In The Terminal](unix/view-a-web-page-in-the-terminal.md)
 - [View The Source For A Brew Formula](unix/view-the-source-for-a-brew-formula.md)

bash/edit-the-current-command-prompt.md

@@ -0,0 +1,18 @@
+# Edit The Current Command Prompt
+
+A neat feature of `bash` is the ability to open whatever the current state of
+the command prompt is into your default editor.
+
+Let's say we have a really long command that we've just tried to run, but it
+failed and we need to make a small change somewhere in the middle. Instead of
+holding the left arrow key for 30 seconds, we can instead hit `CTRL-X CTRL-E`.
+
+This pops us into our `EDITOR` (or maybe `VISUAL`, not sure which). In my case,
+that is `nvim`. I now have access to all the features I'm used to in `nvim` for
+quickly navigating to and editing, searching and replacing, or whatever.
+
+Once I've got the command how I like it, I can save and exit (`:wq`) and the
+updated command will be executed.
+
+This is similar to [the `fc` builtin](unix/fix-previous-command-with-fc.md),
+which also happens to be available for `zsh`.

devops/set-get-and-unset-env-vars-with-dokku.md

@@ -0,0 +1,29 @@
+# Set, Get, And Unset Env Vars With Dokku
+
+The `dokku` CLI provides `config` subcommands for managing environment variables
+for the target container.
+
+An env var can be set for an active container with `config:set`:
+
+```bash
+$ dokku config:set app-name JEMALLOC_ENABLED=true MALLOC_CONF="stats_print:true"
+```
+
+Notice I'm able to set multiple env vars at once if needed.
+
+If I ever need to check what an env var is currently set to for one of my app
+containers, I can use `config:get`:
+
+```bash
+$ dokku config:get app-name JEMALLOC_ENABLED
+true
+```
+
+I can always override any value with another `config:set`. However, if I need to
+entirely remove the env var, I can use `config:unset`:
+
+```bash
+$ dokku config:unset app-name MALLOC_CONF
+```
+
+[source](https://dokku.com/docs/configuration/environment-variables/)

mac/control-which-monitor-app-switcher-appears-on.md

@@ -0,0 +1,21 @@
+# Control Which Monitor App Switcher Appears On
+
+For the most part when I hit `cmd+tab` (and `cmd+shift+tab`) to switch between
+apps, the visual switcher UI (which shows a row of the open apps) appears on my
+main monitor. However, sometimes I will be hitting `cmd+tab` and nothing shows
+up on my main monitor. I look to the right at my side monitor and there is the
+app switcher UI.
+
+Why is it appearing over there all of a sudden?
+
+The reason is that the app switcher UI is anchored to the same screen where the
+doc is located. Though the doc defaults to my main monitor, if I access the doc
+from the side monitor, now it is anchored there.
+
+To switch it back, I just have to make the doc slide up on my main monitor by
+running my mouse down to the bottom of that screen.
+
+The switch up was because I accidentally accessed the doc on my side monitor
+without realizing.
+
+[source](https://superuser.com/a/744680)

mise/override-your-project-mise-file.md

@@ -0,0 +1,37 @@
+# Override Your Project Mise File
+
+A project I'm working on has a version-controlled `.mise.toml` file in it. Some
+changes were made to that recently that introduce some env vars that conflict
+with my setup. If I make edits to that file, then I have a modified version of
+`.mise.toml` sitting in my Git working copy.
+
+```
+# .mise.toml
+[env]
+CONFIG_SETTING = "project"
+```
+
+Instead, I can rely on the loading precedence rules of `mise` to override those
+project settings with my individual settings. I can do that with the
+`.mise.local.toml` file which is played on top of any `mise` configuration from
+files further down the precedence chain.
+
+```
+# .mise.local.toml
+[env]
+CONFIG_SETTING = "override"
+```
+
+Assuming I have `mise` setup with my shell environment to automatically load in
+these files, I can now check what takes precedence:
+
+```bash
+$ echo $CONFIG_SETTING
+override
+```
+
+Make sure `.mise.local.toml` is included in the `.gitignore` file to avoid
+checking in your personal environment overrides.
+
+To be sure about what files are loaded and in what order, give `mise cfg` a try.
+I discuss that in more detail in [List The Files Being Loaded By Mise](list-the-files-being-loaded-by-mise.md).

mise/search-through-bin-paths-for-tool-locations.md

@@ -0,0 +1,29 @@
+# Search Through Bin Paths For Tool Locations
+
+The `mise bin-paths` command will list all the bin paths that are managed by
+`mise`. When you tell `mise` to install a tool, it installs a specific version
+at a location where its binaries can be made accessible on the system path.
+
+While `mise ls` is useful for seeing what is installed by `mise` and at what
+version, the `bin-paths` command can tell you where those tool installations
+with their binaries are located.
+
+Combine this with `grep` or `rg` to narrow down the results to tools by a
+specific name:
+
+```bash
+❯ mise bin-paths | rg 'neovim'
+/Users/lastword/.local/share/mise/installs/npm-neovim/5.4.0/bin
+/Users/lastword/.local/share/mise/installs/pipx-neovim-remote/2.5.1/bin
+/Users/lastword/.local/share/mise/installs/neovim/0.11.6/bin
+```
+
+I can then look in one of these directories to see the one or more binaries that
+they include. For instance, here is what is in the `node` bin path:
+
+```bash
+❯ ls /Users/lastword/.local/share/mise/installs/node/22.22.0/bin
+ ./   ../   claude@   corepack@   node*   npm*   npx@
+```
+
+See `mise bin-paths --help` for more details.

postgres/compute-median-instead-of-average.md

@@ -0,0 +1,44 @@
+# Compute Median Instead Of Average
+
+One of the first aggregate functions we might use in PostgreSQL, besides `sum`,
+is `avg`.
+
+```sql
+select avg(book_count) as average_books_read
+from (
+  select users.id, count(books.id) as book_count
+  from users
+  left join books
+    on books.user_id = users.id
+  where books.read_in_year = 2025
+  group by users.id
+) as user_book_counts;
+```
+
+This computes the average of the set of values which sums them all up
+and divides by the count. The average (maybe you've heard this also called the
+_mean_) is not always the best way to understand data, especially when there are
+outliers.
+
+Instead, we might want to compute the _median_ value of our set of data. There
+is no easily identifiable `median` aggregate function. Instead, we can use
+`percentile_cont` with a value of `0.5`. This gets us the 50th percentile of our
+set of data which is the definition of the _median_.
+
+```sql
+select percentile_cont(0.5) within group (
+  order by book_count
+) as median_books_read
+from (
+  select users.id, count(books.id) as book_count
+  from users
+  left join books on books.user_id = users.id and books.read_in_year = 2025
+  group by users.id
+) as user_book_counts;
+```
+
+The full syntax for `percentile_cont` is `percentile_cong(precision) within
+group (order by ...)` because this is an aggregiate that has to work with an
+ordered-set of data.
+
+[source](https://www.postgresql.org/docs/current/functions-aggregate.html)

python/access-most-recent-return-value-in-repl.md

@@ -0,0 +1,34 @@
+# Access Most Recent Return Value In REPL
+
+One of my favorite features of Ruby's `irb` and `pry` are that you can use `_`
+to reference the most recent return value. Often as we use an interpreter or
+REPL, we end up with _intermediate_ values. That is, we've execute some kind of
+statement which returned a value and we now want to use that resulting value in
+our next statement. Python also supports `_`.
+
+Let's say I've run a statement that took a while to process, but I forgot to
+assign it to a variable. Instead of re-running the whole thing, I can create a
+variable that references the previous return value using `_`.
+
+```python
+>>> BytePairEncoding.train_bpe(long_text)
+{'merge_rules': [...], 'vocab': {...}}
+>>> result = _
+>>> list(result.keys())
+['merge_rules', 'vocab']
+```
+
+Even if I don't necessarily want to assign it a variable, it can be nice to
+reference the previous value as I continue with what I'm doing:
+
+```python
+>>> result['merge_rules'][0][1]
+256
+>>> result['vocab'][_]
+b'e '
+```
+
+Notice how the value from the first statement gets used as part of a `dict`
+access.
+
+[source](https://docs.python.org/3/tutorial/introduction.html#numbers)

python/check-if-package-is-installed-with-pip.md

@@ -0,0 +1,50 @@
+# Check If Package Is Installed With Pip
+
+I recently installed PyTorch, but when I tried using it, I was getting an error
+about `numpy` not being installed. I was kind of surprised by that because I
+thought I would have already had that.
+
+I wanted to check, so I asked with `pip show`:
+
+```bash
+❯ python3 -m pip show numpy
+WARNING: Package(s) not found: numpy
+```
+
+I can even list everything that is installed with `pip` using `pip list` like
+so:
+
+```bash
+❯ python3 -m pip list
+Package            Version   Build
+------------------ --------- -----
+certifi            2026.1.4
+cffi               2.0.0
+charset-normalizer 3.4.4
+click              8.3.1
+commonmark         0.9.1
+cryptography       46.0.3
+docutils           0.22.4
+filelock           3.24.2
+fsspec             2026.2.0
+idna               3.11
+Jinja2             3.1.6
+...
+```
+
+I then installed `numpy` (`python3 -m pip install numpy`) and how I can use `pip
+show` again to confirm that.
+
+```bash
+❯ python3 -m pip show numpy
+Name: numpy
+Version: 2.4.2
+Summary: Fundamental package for array computing in Python
+Home-page: https://numpy.org
+Author: Travis E. Oliphant et al.
+Author-email:
+License-Expression: BSD-3-Clause AND 0BSD AND MIT AND Zlib AND CC0-1.0
+Location: /Users/lastword/.local/share/mise/installs/python/3.12.12/lib/python3.12/site-packages
+Requires:
+Required-by:
+```

python/easy-key-value-aggregates-with-defaultdict.md

@@ -0,0 +1,53 @@
+# Easy Key-Value Aggregates With defaultdict
+
+The `collections` module has the `defaultdict` object that can be used to
+aggregate values tied to a key. What sets this apart from simply using a `dict`
+is that we get the base value for free. So if our aggregate value is a list,
+then we get `[]` by default for each new key. In the same way, we'd get `0` if
+it was constructed with `int`.
+
+Here is the counter example from [Keep A Tally With
+collections.Counter](keep-a-tally-with-collections-counter.md)
+
+```python
+from collections import defaultdict
+
+def get_pair_counts(token_ids: list[int]) -> Counter:
+    """Count how often each adjacent pair appears"""
+    counts = defaultdict(int)
+    for i in range(len(token_ids) - 1):
+        pair = (token_ids[i], token_ids[i + 1])
+        counts[pair] += 1
+    return counts
+```
+
+We never have to initially set a key to `0`. If the key is not yet present, then
+`int()` (the zero-value constructor) is used as the `__missing__` value.
+
+We can do the same with `list`:
+
+```python
+>>> import collections
+>>> stuff = collections.defaultdict(list)
+>>> stuff['alpha'].append(1)
+>>> stuff['alpha']
+[1]
+>>> stuff['beta']
+[]
+```
+
+In the same way, this uses `list()` as the `__missing__` value to start of each
+key with an `[]`.
+
+I find this so handy because in other languages I've typically had to do
+something more like this:
+
+```python
+words_by_length = {}
+for item in items:
+    if len(item) not in words_by_length:
+        words_by_length[len(item)] = []
+    words_by_length[len(item)].append(item)
+```
+
+This is much clunkier.

python/install-with-pip-for-specific-interpreter.md

@@ -0,0 +1,17 @@
+# Install With PIP For Specific Interpreter
+
+The `pip` module can be invoked for any of its commands, such as install, using
+a specific Python interpreter like so:
+
+```bash
+$ python3 -m pip install black
+```
+
+This avoid ambiguity between the version of Python I am using and version of the
+package manager I'm using.
+
+Similarly if I need to upgrade `pip`, I can do the following:
+
+```bash
+$ python3 -m pip install --upgrade pip
+```

python/iterate-first-n-items-from-enumerable.md

@@ -0,0 +1,27 @@
+# Iterate First N Items From Enumerable
+
+As I'm working through the 2nd chapter of [Build a Large Language Model (from
+scratch)](https://still.visualmode.dev/blogmarks/227), I came across a code
+example processing a dictionary of words. This example used a for loop to print
+out each dictionary entry until an index of 50 was reached on then it did a
+`break`.
+
+This struck me as an odd way to grab and process N items from a list. I did some
+searching and found `itertools` which provides
+[`islice`](https://docs.python.org/3/library/itertools.html#itertools.islice).
+
+```python
+from itertools import islice
+
+# preprocess words from a file into a word list
+all_words = ... # not shown here
+
+vocab = {token: integer for integer, token in enumerate(all_words)}
+for item in islice(enumerate(vocab.items()), 50):
+    print(item)
+```
+
+The `islice` function is a better approach because the intention (to grab the
+first 50 things) is encoded in the function call rather than buried in a loop
+body. It also has equivalent memory efficiency to the original example because
+it lazily processes the list of `vocab` items.

python/iterate-over-a-dictionary.md

@@ -0,0 +1,34 @@
+# Iterate Over A Dictionary
+
+Let's say we have a `dict` that contains counts of occurrences for each word in
+some sample text:
+
+```python
+words_frequency = {
+    "the": 4,
+    "a": 3,
+    "dog": 1,
+    "bone": 1,
+    "wants": 1,
+    ...
+}
+```
+
+Here is how we can iterate over the `dict`, accessing both the keys and values:
+
+```python
+for word, count in word_frequency.items():
+    print(f"- {word} appears {count} time{'' if count == 1 else 's'}")
+```
+
+Using the
+[`items()`](https://docs.python.org/3/library/stdtypes.html#dict.items) method,
+we're able to access both _key_ and _value_ with the for loop as it iterates.
+
+Another approach is to loop directly on the `dict` which implicitly surfaces the
+_key_ for iteration. This can then be used to get the value from the `dict`:
+
+```python
+for word in word_frequency:
+    print(f"- {word}: {word_frequency[word]}
+```

python/keep-a-tally-with-collections-counter.md

@@ -0,0 +1,40 @@
+# Keep A Tally With collections.Counter
+
+Python's `collections` module comes with a
+[`Counter`](https://docs.python.org/3/library/collections.html#collections.Counter)
+object which is a specialized dict subclass focussed on tallying counts of keys.
+
+> It is a collection where elements are stored as dictionary keys and their
+> counts are stored as dictionary values. Counts are allowed to be any integer
+> value including zero or negative counts.
+
+I used it recently while doing an exploratory implementation of a Byte-Pair
+Encoding (BPE):
+
+```python
+from collections import Counter
+
+def get_pair_counts(token_ids: list[int]) -> Counter:
+    """Count how often each adjacent pair appears"""
+    counts = Counter()
+    for i in range(len(token_ids) - 1):
+        pair = (token_ids[i], token_ids[i + 1])
+        counts[pair] += 1
+    return counts
+```
+
+Here I'm able to count the number of occurrences of each pair of bytes from the
+input text. A tuple of `int` values is hashable, so they work great as keys for
+a `Counter`.
+
+The count value of any key will default to `0`. That makes it straightforward to
+increment from there as you iterating over occurrences.
+
+```python
+>>> counts = Counter()
+>>> counts['hello']
+0
+>>> count['hello'] += 1
+>>> count['hello']
+1
+```

python/load-a-file-into-the-python-repl.md

@@ -0,0 +1,35 @@
+# Load A File Into The Python REPL
+
+I opened up a Python REPL to try some things out.
+
+```
+$ python3
+>>> import math
+>>> math.floor(5/2)
+2
+```
+
+Now, I want to reference a Python file I've been working on so that I can
+manually test the behavior of what I'm building. To do this, I can import a file
+by its name in the same way that I would import any module. Then I can use that
+namespace for class and method references. Crucially, the file should exist in
+the same directory the REPL was started from.
+
+First, here is the file:
+
+```python
+# bpe.py
+class BytePairEncoding:
+    def text_to_bytes(text: str) -> list[int]:
+        """Convert a string to a list of byte values (0-255)"""
+        return list(text.encode("utf-8"))
+```
+
+Now to use it from the REPL:
+
+```
+$ python
+>>> import bpe
+>>> bpe.BytePairEncoding.text_to_bytes("Gimme some bytes!")
+[71, 105, 109, 109, 101, 32, 115, 111, 109, 101, 32, 98, 121, 116, 101, 115, 33]
+```

rails/check-how-database-is-configured.md

@@ -0,0 +1,46 @@
+# Check How Database Is Configured
+
+While making some adjustments to the database connection string (`DATABASE_URL`)
+for a pre-production Rails environment, we wanted to check that configuration
+options like `sslmode` were picked up.
+
+From a `rails console` session I can check the live database configuration like
+so:
+
+```ruby
+> ActiveRecord::Base.connection_db_config.configuration_hash
+=> {
+  adapter: "postgresql",
+  encoding: "unicode",
+  pool: 5,
+  database: "my_app_development"
+}
+```
+
+I can look at the
+[`configuration_hash`](https://api.rubyonrails.org/classes/ActiveRecord/DatabaseConfigurations/HashConfig.html#attribute-i-configuration_hash)
+from `rails console` of my pre-prod environment to see more configuration
+settings:
+
+```ruby
+> ActiveRecord::Base.connection_db_config.configuration_hash
+=> {
+  adapter: "postgresql",
+  encoding: "unicode",
+  pool: 5,
+  username: "app_user",
+  password: "super_s3cr3t",
+  port: 15432,
+  database: "pre_prod_database",
+  host: "some-host-123.ondigitalocean.com",
+  sslmode: "verify-full"
+}
+```
+
+Since I was specifically looking for the `sslmode` value, I can access that
+directly:
+
+```ruby
+> ActiveRecord::Base.connection_db_config.configuration_hash[:sslmode]
+=> "verify-full"
+```

rails/check-the-current-named-log-level.md

@@ -0,0 +1,46 @@
+# Check The Current Named Log Level
+
+I'm connected to a `rails console` session for an active Rails app. I want to
+check the current log level.
+
+```ruby
+> Rails.logger.level
+=> 1
+```
+
+The `1` doesn't mean much to me at a glance. I can translate that to the
+severity level using the `Logger::SEV_LABLE` constant.
+
+```ruby
+[44] pry(main)> Logger::SEV_LABEL[Rails.logger.level]
+=> "INFO"
+```
+
+Ah yes, `INFO`, that makes sense as the default.
+
+I can see all the severity levels by inspecting the constant itself.
+
+```ruby
+[45] pry(main)> Logger::SEV_LABEL
+=> ["DEBUG", "INFO", "WARN", "ERROR", "FATAL", "ANY"]
+```
+
+As I convenience, I can set the label using the index, the string, or even a
+symbol.
+
+```ruby
+> Rails.logger.level
+=> 1
+> Rails.logger.level = "WARN"
+=> "WARN"
+> Rails.logger.level
+=> 2
+> Rails.logger.level = :debug
+=> :debug
+> Rails.logger.level
+=> 0
+```
+
+See the [Debugging Rails Applications
+guide](https://guides.rubyonrails.org/debugging_rails_applications.html#log-levels)
+for more details.

rails/clean-up-memory-hungry-rails-console-processes.md

@@ -0,0 +1,43 @@
+# Clean Up Memory Hungry Rails Console Processes
+
+I noticed (using `htop`) that a remote server hosting a Rails app had most of
+its RAM being actively consumed. This was hindering my ability to run a fresh
+deploy because the deploy processes had to do a ton of memory swapping which
+drastically slowed the whole thing down.
+
+With some investigation, I discovered that most of the memory was being consumed
+by a handful of `rails console` processes. I didn't have any known active `rails console` processes that I was using. That combined with the dates of these
+processes starting way in the past suggested to me that these were abandoned
+processes that hadn't been properly cleaned up.
+
+```bash
+server:~# ps aux | grep rails
+32767     878915  0.0  0.0 1227160  936 pts/0    Ssl+  2025   0:03 /exec rails console
+32767     878942  0.9  6.5 830996 261748 pts/0   Rl+   2025 249:51 ruby /app/bin/rails console
+32767    3004097  0.0  0.0 1227160  692 pts/0    Ssl+  2025   0:04 /exec rails console
+32767    3004129  0.9  6.4 834672 257228 pts/0   Dl+   2025 406:31 ruby /app/bin/rails console
+32767    3048582  0.0  0.0 1227160  940 pts/0    Ssl+ Jan09   0:00 /exec rails console
+32767    3048611  1.1  6.3 829936 253484 pts/0   Dl+  Jan09  60:50 ruby /app/bin/rails console
+32767    3060033  0.0  0.0 1227160  944 pts/0    Ssl+  2025   0:04 /exec rails console
+32767    3060063  0.9  6.5 838084 260812 pts/0   Rl+   2025 405:37 ruby /app/bin/rails console
+root     3699372  0.0  0.0   7008  1300 pts/0    S+   15:51   0:00 grep --color=auto rails
+server:~# ps aux | grep 'rails console' | awk '{sum+=$6} END {print sum/1024 " MB"}'
+1014.64 MB
+```
+
+As we can see by tacking on this `awk` command, these processes are consuming
+1GB of memory.
+
+Each of these is a pair of processes. A parent process (`/exec rails console`)
+that kicks off and supervises the memory-hungry child process (`ruby /app/bin/rails console`).
+
+To free up this memory, I targeted each of the parent processes with a `kill`
+command one by one. For example:
+
+```bash
+server:~# kill 878915
+```
+
+I suspect that I may have left the occasional terminal tab open with one of
+these `rails console` processes running and the SSH connection was getting
+killed without the `rails console` getting killed with it.

ruby/make-a-long-string-of-text-readable.md

@@ -0,0 +1,38 @@
+# Make A Long String Of Text Readable
+
+I have a paragraph of text that interpolates a couple user-specific values
+before being included in an API request. Because it is being passed to an API,
+it is a single-line string value. However, in the editor it is hard to read like
+that because it overflows way past the edge of the viewport.
+
+```ruby
+description = "This is the description we need to provide for #{user.name} as part of an API request dealing with compliance and registration for a service. If you need to contact them, their email is #{user.email}."
+```
+
+I'd rather make this easier on myself and others to read from the editor while
+still being able to submit a single-line string to the API. That can be
+accomplished with a heredoc and some combination or `gsub`, `strip`, and
+`squish`.
+
+If we are in a strictly Ruby-only context, we can use `gsub` and `strip` to
+collapse line breaks and remove surrounding white space.
+
+```ruby
+description = <<~MSG.gsub(/\s+/, ' ').strip
+  This is the description we need to provide for #{user.name} as part
+  of an API request dealing with compliance and registration for a
+  service. If you need to contact them, their email is #{user.email}.
+MSG
+#=> "This is the description we need to provide for #{user.name} as part of an API request dealing with compliance and registration for a service. If you need to contact them, their email is #{user.email}."
+```
+
+Or in a Rails context, I can instead just use `squish`:
+
+```ruby
+description = <<~MSG.squish
+  This is the description we need to provide for #{user.name} as part
+  of an API request dealing with compliance and registration for a
+  service. If you need to contact them, their email is #{user.email}.
+MSG
+#=> "This is the description we need to provide for #{user.name} as part of an API request dealing with compliance and registration for a service. If you need to contact them, their email is #{user.email}."
+```

ruby/specify-default-for-data-definition.md

@@ -0,0 +1,43 @@
+# Specify Default For Data Definition
+
+Here is what a `Data` definition for the concept of a `Permission` might look
+like:
+
+```ruby
+Permission = Data.define(:id, :name, :description, :enabled)
+
+perm1 = Permission.new(
+  id: 123,
+  name: :can_edit,
+  description: "User is allowed to edit.",
+  enabled: true
+)
+```
+
+However, as we're creating various `Permission` entities, we may find that the
+vast majority of them are _enabled_ by default and so we'd like to apply `true`
+as a default value.
+
+We cannot do this directly in the `Data` definition, but we can open a block to
+override the `initialize` method.
+
+```ruby
+Permission = Data.define(:id, :name, :description, :enabled) do
+  def initialize(:id, :name, :description, enabled: true)
+    super
+  end
+end
+
+perm1 = Permission.new(
+  id: 123,
+  name: :can_edit,
+  description: "User is allowed to edit."
+)
+
+perm1.enabled #=> true
+```
+
+Now we're able to create a `Permission` without specifying the `enabled`
+attribute and it takes on the default of `true`.
+
+[source](https://dev.to/baweaver/new-in-ruby-32-datadefine-2819#comment-254o8)

tmux/list-processes-running-across-all-sessions.md

@@ -0,0 +1,46 @@
+# List Processes Running Across All Session
+
+I wanted an overview of all the processes running across all the tmux sessions
+that I have running on my machine right now. The `list-panes` command (with the
+`-a` flag) gives me a listing of all the panes across all session of the current
+tmux server.
+
+That output on its own isn't giving me quite the info I'm looking for though.
+With the `-f` (_format_) flag, I can use variables available in that context
+like `session_name`, `pane_pid`, and `pane_current_command`.
+
+I can assemble the details I want into a command like this:
+
+```bash
+❯ tmux list-panes -a -F "#{session_name}:#{window_index}.#{pane_index} #{pane_pid} #{pane_current_command}"
+PLP:1.1 62364 zsh
+TIL:1.1 62345 nvim
+TIL:1.2 65838 task
+TIL:2.1 11428 tmux
+client-app:1.1 62373 ssh
+client-app:1.2 10796 zsh
+client-app:1.3 63081 zsh
+client-app:2.1 61115 overmind
+client-app:3.1 82608 zsh
+visualmode-dev:1.1 52237 zsh
+```
+
+This gives me the details I want, but I can take it a step further by piping it
+to the `column` command to improve the formatting a little:
+
+```bash
+❯ tmux list-panes -a -F "#{session_name}:#{window_index}.#{pane_index} #{pane_pid} #{pane_current_command}" \
+  | column -t
+PLP:1.1             62364  zsh
+TIL:1.1             62345  nvim
+TIL:1.2             65838  task
+TIL:2.1             11428  tmux
+client-app:1.1      62373  ssh
+client-app:1.2      10796  zsh
+client-app:1.3      63081  zsh
+client-app:2.1      61115  overmind
+client-app:3.1      82608  zsh
+visualmode-dev:1.1  52237  zsh
+```
+
+See `man tmux` and, in particular, the `FORMATS` section for more details.

unix/combine-all-my-tils-into-a-single-file.md

@@ -0,0 +1,35 @@
+# Combine All My TILs Into A Single File
+
+In [Build A Small Text-based Training
+Dataset](https://www.visualmode.dev/build-a-small-text-training-dataset), I went
+over my need for a sizeable and interesting corpus of text that I could use as a
+training dataset I could use to run against [my own naive Byte Pair Encoding
+implementation](https://github.com/jbranchaud/build-an-llm-from-scratch/blob/main/chapter-02/bpe_tokenizer.py).
+My repo of hand-written TILs is a great candidate, but I need those smashed all
+into one file.
+
+Here is a formatted version of the one-liner I ended up with:
+
+```bash
+{
+  cat README.md; \
+  find */ -name '*.md' -print0 \
+  | sort -z \
+  | xargs -0 -I{} sh -c 'echo "<|endoftext|>"; cat "$1"' _ {}; \
+} > combined.md
+```
+
+This combines all 1700+ of my TILs into a single file separated by the
+`<|endoftext|>` delimiter.
+
+The two things I find most interesting about this command are:
+
+1. The use of a null byte (`\0`) separator between the filenames in case there
+   is anything weird (like spaces) in those filenames. This starts with
+   `-print0`. The `-z` of `sort` maintains that null byte separator. And then
+   `xargs` knows to handle it by the `-0` flag.
+
+2. We can coerce `xargs` into running multiple commands by having it spawn a
+   single shell process that runs each of those commands. To reliably pass the
+   filename into that shell process, we have `xargs` constitute it as the second
+   argument (`$1`) by substituting in the filename where `{}` appears.

unix/format-and-display-small-amounts-of-columnar-data.md

@@ -0,0 +1,44 @@
+# Format And Display Small Amounts Of Columnar Data
+
+In [_List Processes Running Across All (tmux)
+Sessions](tmux/list-processes-running-across-all-sessions.md), I showed an
+example of piping some data from `tmux` to the `column -t` command to nicely format
+and display the columnar data as a table. By default is uses spaces as the
+delimiter.
+
+```bash
+❯ tmux list-panes -a -F "#{session_name}:#{window_index}.#{pane_index} #{pane_pid} #{pane_current_command}" \
+  | column -t
+
+PLP:1.1             62364  zsh
+TIL:1.1             62345  nvim
+TIL:1.2             65838  task
+TIL:2.1             11428  tmux
+client-app:1.1      62373  ssh
+client-app:1.2      10796  zsh
+client-app:1.3      63081  zsh
+client-app:2.1      61115  overmind
+client-app:3.1      82608  zsh
+visualmode-dev:1.1  52237  zsh
+```
+
+This can be useful for formatting data from all kinds of commands and tools.
+Sometimes the columns of data are separated by something other than spaces. For
+instance, here is some git branch information (for my [dotfiles
+repo](https://github.com/jbranchaud/dotfiles)) separated by the `|` character.
+To format that with `column`, I need to also include the `-s '|'` flag to
+override the delimiter.
+
+```bash
+❯ git for-each-ref --format='%(refname:short)|%(authordate:short)|%(authorname)' refs/heads/ \
+  | column -t -s '|'
+
+claude/sync-dotfiles-011CUP87cRV6c51eEi3Chg99  2025-10-22  jbranchaud
+jb/add-rhubarb-for-fugitive-github-browse      2025-11-02  jbranchaud
+jb/fix-hardcoded-paths                         2025-11-02  jbranchaud
+jb/set-nvim-to-default-manpager                2025-10-19  jbranchaud
+main                                           2026-01-10  jbranchaud
+master                                         2025-10-30  Dorian Karter
+my-dotfiles                                    2025-11-01  jbranchaud
+upstream-master                                2026-01-01  Dorian Karter
+```

unix/inspect-exif-data-for-an-image-file.md

@@ -0,0 +1,47 @@
+# Inspect EXIF Data For An Image File
+
+The `exiftool` CLI (which can be downloaded via `brew`) is a useful tool for
+inspecting all the EXIF data attached to a media file. A media file like an
+image has a bunch of additional details embedded in it like timestamps, image
+metadata, and sometimes location information.
+
+Here is all the data attached to a screenshot I found on my desktop:
+
+```bash
+❯ exiftool ~/Desktop/CleanShot\ 2025-11-17\ at\ 11.22.18@2x.png
+ExifTool Version Number         : 13.50
+File Name                       : CleanShot 2025-11-17 at 11.22.18@2x.png
+Directory                       : /Users/lastword/Desktop
+File Size                       : 1194 kB
+File Modification Date/Time     : 2025:11:17 11:22:21-06:00
+File Access Date/Time           : 2025:12:15 10:43:55-06:00
+File Inode Change Date/Time     : 2025:12:05 15:37:48-06:00
+File Permissions                : -rw-r--r--
+File Type                       : PNG
+File Type Extension             : png
+MIME Type                       : image/png
+Image Width                     : 2502
+Image Height                    : 1232
+Bit Depth                       : 8
+Color Type                      : RGB with Alpha
+Compression                     : Deflate/Inflate
+Filter                          : Adaptive
+Interlace                       : Noninterlaced
+XMP Toolkit                     : XMP Core 6.0.0
+Y Resolution                    : 144
+Resolution Unit                 : inches
+X Resolution                    : 144
+Exif Image Width                : 2502
+Color Space                     : sRGB
+User Comment                    : Screenshot
+Exif Image Height               : 1232
+SRGB Rendering                  : Perceptual
+Image Size                      : 2502x1232
+Megapixels                      : 3.1
+```
+
+This works with other kinds of media files. For instance, I ran this against an
+MP4 screen recording file which contained even more metadata.
+
+In addition to reading data, `exiftool` can also write it. See `man exiftool`
+for more details on what else it can do.

unix/show-tree-view-of-processes-and-subprocesses.md

@@ -0,0 +1,36 @@
+# Show Tree View Of Processes And Subprocesses
+
+Though you can cobble together a command on a MacOS Unix system to output a
+hierarchical tree view of a parent process and its descendent subprocesses, it
+is easier to [`brew install pstree`](https://github.com/FredHucht/pstree) and
+use that.
+
+Here is what I see when I run it for a _pid_ that corresponds to a `tmux`
+session that I have running locally:
+
+```bash
+❯ pstree 61690
+-+= 61690 lastword tmux new-session -d -s TIL -c /Users/lastword/dev/jbranchaud/til
+ |--= 63081 lastword /bin/zsh
+ |-+= 11428 lastword zsh
+ | \-+= 48511 lastword pstree 61690
+ |   \--- 48512 root ps -axwwo user,pid,ppid,pgid,command
+ |-+= 62345 lastword zsh
+ | \--= 06031 lastword claude
+ |--= 62364 lastword /bin/zsh
+ |-+= 62373 lastword zsh
+ | \--= 64407 lastword ssh my-app-staging
+ |-+= 61115 lastword /bin/zsh
+ | \-+= 61579 lastword overmind start -f Procfile.dev
+ |   \--- 61586 lastword tmux -C -L overmind-my-app-abc123 new -n web -s my-app -P -F %overmind-process #{pane_id} web #{pane_pid} /var/folders/zc/abc123/T/overmin
+ |--= 52237 lastword /bin/zsh
+ |--= 82608 lastword /bin/zsh
+ \--= 10796 lastword /bin/zsh
+```
+
+I was looking for a frozen `claude` process that was part of this session. And I
+found it about halfway down that list -- `06031`. Now I can run `kill` on that
+process as needed.
+
+For some additional context, I initially found the _pid_ for the `tmux` session
+by running `ps aux | grep tmux` and looking through those results.

unix/use-negative-lookbehind-matching-with-ripgrep.md

@@ -0,0 +1,42 @@
+# Use Negative Lookbehind Matching With ripgrep
+
+The most straightforward way to use `ripgrep` is to hand it a pattern. It will
+take that pattern and move forward through each file trying to find matches.
+
+```bash
+$ rg 'TwilioClient\.new'
+```
+
+That will find all occurrences of `TwilioClient.new` in available project files.
+
+What if that pattern is too permissive though? That is going to match on
+occurrences of `TwilioClient.new` as well as things like
+`LoggingTwilioClient.new`. If we want to exclude the latter, there are a few
+ways to do that. One of them being the use of [the _negative lookbehind_ regex
+feature](https://www.pcre.org/current/doc/html/pcre2syntax.html#SEC23) that is
+available with PCRE2 (Perl-Compatible Regular Expressions).
+
+A _negative lookbehind_ is like a standard pattern. We look forward through the
+document for the base pattern (like `TwilioClient\.new`). However, once we find
+that match, we then look back at the previous characters and if they match our
+negative lookbehind pattern, then it is no longer a positive match.
+
+We can use one of the following to forms to achieve this:
+
+```
+  (?<!...)                    )
+  (*nlb:...)                  ) negative lookbehind
+  (*negative_lookbehind:...)  )
+```
+
+For instance, here is what this looks like for our example:
+
+```bash
+$ rg -P '(?<!Logging)TwilioClient\.new'
+```
+
+Note: we have to use the `-P` flag to tell `ripgrep` that we are using PCRE2
+syntax. Otherwise, it assumes a simpler regex syntax that doesn't support
+_negative lookbehind_.
+
+See `man rg` for more details.