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6984685276
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6984685276 |
@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
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For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
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For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
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_1510 TILs and counting..._
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_1508 TILs and counting..._
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---
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---
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@@ -888,7 +888,6 @@ _1510 TILs and counting..._
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- [Access Instance Variables](python/access-instance-variables.md)
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- [Access Instance Variables](python/access-instance-variables.md)
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- [Create A Dummy DataFrame In Pandas](python/create-a-dummy-dataframe-in-pandas.md)
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- [Create A Dummy DataFrame In Pandas](python/create-a-dummy-dataframe-in-pandas.md)
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- [Dunder Methods](python/dunder-methods.md)
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- [Dunder Methods](python/dunder-methods.md)
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- [Override The Boolean Context Of A Class](python/override-the-boolean-context-of-a-class.md)
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- [Store And Access Immutable Data In A Tuple](python/store-and-access-immutable-data-in-a-tuple.md)
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- [Store And Access Immutable Data In A Tuple](python/store-and-access-immutable-data-in-a-tuple.md)
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- [Test A Function With Pytest](python/test-a-function-with-pytest.md)
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- [Test A Function With Pytest](python/test-a-function-with-pytest.md)
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- [Use pipx To Install End User Apps](python/use-pipx-to-install-end-user-apps.md)
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- [Use pipx To Install End User Apps](python/use-pipx-to-install-end-user-apps.md)
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@@ -1222,7 +1221,6 @@ _1510 TILs and counting..._
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- [Find The Min And Max With A Single Call](ruby/find-the-min-and-max-with-a-single-call.md)
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- [Find The Min And Max With A Single Call](ruby/find-the-min-and-max-with-a-single-call.md)
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- [Finding The Source of Ruby Methods](ruby/finding-the-source-of-ruby-methods.md)
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- [Finding The Source of Ruby Methods](ruby/finding-the-source-of-ruby-methods.md)
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- [Format A Hash Into A String Template](ruby/format-a-hash-into-a-string-template.md)
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- [Format A Hash Into A String Template](ruby/format-a-hash-into-a-string-template.md)
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- [Forward All Arguments To Another Method](ruby/forward-all-arguments-to-another-method.md)
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- [Generate A Signed JWT Token](ruby/generate-a-signed-jwt-token.md)
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- [Generate A Signed JWT Token](ruby/generate-a-signed-jwt-token.md)
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- [Generate Ruby Version And Gemset Files With RVM](ruby/generate-ruby-version-and-gemset-files-with-rvm.md)
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- [Generate Ruby Version And Gemset Files With RVM](ruby/generate-ruby-version-and-gemset-files-with-rvm.md)
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- [Get Info About Your RubyGems Environment](ruby/get-info-about-your-ruby-gems-environment.md)
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- [Get Info About Your RubyGems Environment](ruby/get-info-about-your-ruby-gems-environment.md)
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@@ -1,86 +0,0 @@
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# Override The Boolean Context Of A Class
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Everything in Python has a truthiness that can be checked with `bool()`. An
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empty list (`[]`) is falsy. A non-empty list (`[1,2,3]`) is truthy. Similar
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with numbers:
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```python
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>>> bool(0)
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False
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>>> bool(1)
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True
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```
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Any instance of an object is going to be truthy by default. If you want to
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control in what context an instance is considered truthy or falsy, you can
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override
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[`__bool__()`](https://docs.python.org/3/reference/datamodel.html#object.__bool__).
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If that's not implemented, but
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[`__len__()`](https://docs.python.org/3/reference/datamodel.html#object.__len__)
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is, then it will fallback to that.
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Let's look at a few example classes:
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```python
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class CartZero:
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def __init__(self, items=[]):
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self.items = items or []
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class CartBool:
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def __init__(self, items=[]):
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self.items = items or []
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def __bool__(self):
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print("__bool__() override")
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return bool(self.items)
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class CartLen:
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def __init__(self, items=[]):
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self.items = items or []
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def __len__(self):
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print("__len__() override")
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return len(self.items)
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class CartBoolAndLen:
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def __init__(self, items=[]):
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self.items = items or []
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def __len__(self):
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print("__len__() override")
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return len(self.items)
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def __bool__(self):
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print("__bool__() override")
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return bool(self.items)
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cart1 = CartZero()
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cart2 = CartBool()
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cart3 = CartLen()
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cart4 = CartBoolAndLen()
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print("CartZero() -> %s" %(bool(cart1)))
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print('')
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print("CartBool() -> %s" %(bool(cart2)))
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print('')
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print("CartLen() -> %s" %(bool(cart3)))
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print('')
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print("CartBoolAndLen() -> %s" %(bool(cart4)))
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```
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An 'empty' `Cart` be default is truthy. However, we can override some
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combination of `__bool__()` or `__len__()` to give it a boolean context that
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goes `false` when "empty".
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```
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CartZero() -> True
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__bool__() override
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CartBool() -> False
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__len__() override
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CartLen() -> False
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__bool__() override
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CartBoolAndLen() -> False
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```
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@@ -1,45 +0,0 @@
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# Forward All Arguments To Another Method
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There are three types of arguments that a Ruby method can receive. Positional
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arguments, keyword arguments, and a block argument.
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A method that deals with all three might be defined like this:
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```ruby
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def forwarding_method(*args, **kwargs, &block)
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# implementation
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end
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```
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Now lets say we have some concrete method that we want to forward these
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arguments to:
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```ruby
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def concrete_method(*args, **kwargs)
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x = args.first || 1
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key, y = kwargs.first || [:a, 2]
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puts "Dealing with #{x} and key #{key}: #{y}"
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yield(x, y)
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end
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```
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We could forward arguments the longhand way like this:
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```ruby
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def forwarding_method(*args, **kwargs, &block)
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concrete_method(*args, **kwargs, &block)
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end
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```
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However, since Ruby 2.7 we have access to a shorthand "triple-dot" syntax for
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forwarding all arguments.
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```ruby
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def forwarding_method(...)
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concrete_method(...)
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end
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```
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[source](https://ruby-doc.org/3.3.6/syntax/methods_rdoc.html#label-Argument+Forwarding)
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