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Expand a bit on genexp scopes.

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Georg Brandl 2008-03-03 21:31:50 +00:00
parent d2f7680b8f
commit 8e67ef52db
1 changed files with 9 additions and 8 deletions
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Doc/reference/expressions.rst
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@ -230,14 +230,15 @@ generator are those that would be produced by considering each of the
evaluating the expression to yield a value that is reached the innermost block evaluating the expression to yield a value that is reached the innermost block
for each iteration. for each iteration.
Variables used in the generator expression are evaluated lazily when the Variables used in the generator expression are evaluated lazily in a separate
:meth:`next` method is called for generator object (in the same fashion as scope when the :meth:`next` method is called for the generator object (in the
normal generators). However, the leftmost :keyword:`for` clause is immediately same fashion as for normal generators). However, the :keyword:`in` expression
evaluated so that error produced by it can be seen before any other possible of the leftmost :keyword:`for` clause is immediately evaluated in the current
scope so that an error produced by it can be seen before any other possible
error in the code that handles the generator expression. Subsequent error in the code that handles the generator expression. Subsequent
:keyword:`for` clauses cannot be evaluated immediately since they may depend on :keyword:`for` and :keyword:`if` clauses cannot be evaluated immediately since
the previous :keyword:`for` loop. For example: ``(x*y for x in range(10) for y they may depend on the previous :keyword:`for` loop. For example:
in bar(x))``. ``(x*y for x in range(10) for y in bar(x))``.
The parentheses can be omitted on calls with only one argument. See section The parentheses can be omitted on calls with only one argument. See section
:ref:`calls` for the detail. :ref:`calls` for the detail.