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Fix naming and confusing example in gotchas #265

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Merged
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Apr 14, 2013
Merged

Fix naming and confusing example in gotchas #265

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5da8f3e
gotchas: fix naming; remove generator in def example
simon-weber Apr 3, 2013
aa25ef5
merge upstream
simon-weber Apr 3, 2013
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18 changes: 11 additions & 7 deletions docs/writing/gotchas.rst
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Expand Up @@ -142,28 +142,32 @@ fact the same exact behavior is exhibited by just using an ordinary ``def``:

.. code-block:: python

def create_adders():
def create_multipliers():
multipliers = []

for i in range(5):
def adder(x):
def multiplier(x):
return i * x
yield adder
multipliers.append(multiplier)

return multipliers

What You Should Do Instead
~~~~~~~~~~~~~~~~~~~~~~~~~~

Well. Here the general solution is arguably a bit of a hack. Due to Python's
aforementioned behavior concerning evaluating default arguments to functions
The most general solution is arguably a bit of a hack. Due to Python's
afformentioned behavior concerning evaluating default arguments to functions
(see :ref:`default_args`), you can create a closure that binds immediately to
its arguments by using a default arg like so:

.. code-block:: python

def create_adders():
def create_multipliers():
return [lambda x, i=i : i * x for i in range(5)]

When the Gotcha Isn't a Gotcha
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

When you want your closures to behave this way. Late binding is good in lots of
Sometimes you want your closures to behave this way. Late binding is good in lots of
situations. Looping to create unique functions is unfortunately a case where
they can cause hiccups.