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Nuno Vieira
6984685276 Merge 460473a87f into 877537228f 2024-11-16 17:08:36 +01:00
3 changed files with 1 additions and 134 deletions

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@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
_1510 TILs and counting..._
_1508 TILs and counting..._
---
@@ -888,7 +888,6 @@ _1510 TILs and counting..._
- [Access Instance Variables](python/access-instance-variables.md)
- [Create A Dummy DataFrame In Pandas](python/create-a-dummy-dataframe-in-pandas.md)
- [Dunder Methods](python/dunder-methods.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)
- [Use pipx To Install End User Apps](python/use-pipx-to-install-end-user-apps.md)
@@ -1222,7 +1221,6 @@ _1510 TILs and counting..._
- [Find The Min And Max With A Single Call](ruby/find-the-min-and-max-with-a-single-call.md)
- [Finding The Source of Ruby Methods](ruby/finding-the-source-of-ruby-methods.md)
- [Format A Hash Into A String Template](ruby/format-a-hash-into-a-string-template.md)
- [Forward All Arguments To Another Method](ruby/forward-all-arguments-to-another-method.md)
- [Generate A Signed JWT Token](ruby/generate-a-signed-jwt-token.md)
- [Generate Ruby Version And Gemset Files With RVM](ruby/generate-ruby-version-and-gemset-files-with-rvm.md)
- [Get Info About Your RubyGems Environment](ruby/get-info-about-your-ruby-gems-environment.md)

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@@ -1,86 +0,0 @@
# Override The Boolean Context Of A Class
Everything in Python has a truthiness that can be checked with `bool()`. An
empty list (`[]`) is falsy. A non-empty list (`[1,2,3]`) is truthy. Similar
with numbers:
```python
>>> bool(0)
False
>>> bool(1)
True
```
Any instance of an object is going to be truthy by default. If you want to
control in what context an instance is considered truthy or falsy, you can
override
[`__bool__()`](https://docs.python.org/3/reference/datamodel.html#object.__bool__).
If that's not implemented, but
[`__len__()`](https://docs.python.org/3/reference/datamodel.html#object.__len__)
is, then it will fallback to that.
Let's look at a few example classes:
```python
class CartZero:
def __init__(self, items=[]):
self.items = items or []
class CartBool:
def __init__(self, items=[]):
self.items = items or []
def __bool__(self):
print("__bool__() override")
return bool(self.items)
class CartLen:
def __init__(self, items=[]):
self.items = items or []
def __len__(self):
print("__len__() override")
return len(self.items)
class CartBoolAndLen:
def __init__(self, items=[]):
self.items = items or []
def __len__(self):
print("__len__() override")
return len(self.items)
def __bool__(self):
print("__bool__() override")
return bool(self.items)
cart1 = CartZero()
cart2 = CartBool()
cart3 = CartLen()
cart4 = CartBoolAndLen()
print("CartZero() -> %s" %(bool(cart1)))
print('')
print("CartBool() -> %s" %(bool(cart2)))
print('')
print("CartLen() -> %s" %(bool(cart3)))
print('')
print("CartBoolAndLen() -> %s" %(bool(cart4)))
```
An 'empty' `Cart` be default is truthy. However, we can override some
combination of `__bool__()` or `__len__()` to give it a boolean context that
goes `false` when "empty".
```
CartZero() -> True
__bool__() override
CartBool() -> False
__len__() override
CartLen() -> False
__bool__() override
CartBoolAndLen() -> False
```

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@@ -1,45 +0,0 @@
# Forward All Arguments To Another Method
There are three types of arguments that a Ruby method can receive. Positional
arguments, keyword arguments, and a block argument.
A method that deals with all three might be defined like this:
```ruby
def forwarding_method(*args, **kwargs, &block)
# implementation
end
```
Now lets say we have some concrete method that we want to forward these
arguments to:
```ruby
def concrete_method(*args, **kwargs)
x = args.first || 1
key, y = kwargs.first || [:a, 2]
puts "Dealing with #{x} and key #{key}: #{y}"
yield(x, y)
end
```
We could forward arguments the longhand way like this:
```ruby
def forwarding_method(*args, **kwargs, &block)
concrete_method(*args, **kwargs, &block)
end
```
However, since Ruby 2.7 we have access to a shorthand "triple-dot" syntax for
forwarding all arguments.
```ruby
def forwarding_method(...)
concrete_method(...)
end
```
[source](https://ruby-doc.org/3.3.6/syntax/methods_rdoc.html#label-Argument+Forwarding)