mirror of
https://github.com/jbranchaud/til
synced 2026-07-02 23:58:25 +00:00
jbranchaud
34 lines
1.3 KiB
Markdown
34 lines
1.3 KiB
Markdown
# Sort Normalized Version Of Data
|
|
|
|
Let's say I have a list of names that I want to sort. However, because of
|
|
inconsistency in how the data was entered, sometimes those names are capitalized
|
|
and other times they are not. Using
|
|
[`methodcaller`](https://docs.python.org/3/library/operator.html#operator.methodcaller),
|
|
I can normalize the sorting `key` used when comparing list items.
|
|
|
|
First, let's look at calling `sorted` with the list and no `key`:
|
|
|
|
```python
|
|
>>> sorted(["butler", "Jemisin", "le guin", "Erdrich"])
|
|
['Erdrich', 'Jemisin', 'butler', 'le guin']
|
|
```
|
|
|
|
`butler` which starts with a `b` gets moved to the 3rd position because it is
|
|
lowercase.
|
|
|
|
To sort this list using a normalized comparison, we will use `methodcaller` to
|
|
create a callable out of `lower` which is then passed as the sort `key`:
|
|
|
|
```python
|
|
>>> from operator import methodcaller
|
|
>>> sorted(["butler", "Jemisin", "le guin", "Erdrich"], key=methodcaller("lower"))
|
|
['butler', 'Erdrich', 'Jemisin', 'le guin']
|
|
```
|
|
|
|
That's the sort order I was originally hoping for.
|
|
|
|
What `methodcaller` is doing is creating a callable function that will invoke
|
|
`lower` with each string instance as the target. Conceptually similar to
|
|
`"Erdrich".lower()` or even `getattr("Erdrich", "lower")()` (notice this needs
|
|
to be immediately invoked).
|