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| author | R David Murray <rdmurray@bitdance.com> | 2014-10-01 01:26:24 (GMT) |
|---|---|---|
| committer | R David Murray <rdmurray@bitdance.com> | 2014-10-01 01:26:24 (GMT) |
| commit | bbf4ae51e454b64d3b9408b4b4626a52d7175743 (patch) | |
| tree | 38bfdbf36311c864ba73efdfc44ecb2c69b8aff7 | |
| parent | 5a789f7eaf81c2908bfea42c7ac721800e08a8c8 (diff) | |
| parent | 6bd68608ffb1a0366760a190864bb05c618559ab (diff) | |
| download | cpython-bbf4ae51e454b64d3b9408b4b4626a52d7175743.zip cpython-bbf4ae51e454b64d3b9408b4b4626a52d7175743.tar.gz cpython-bbf4ae51e454b64d3b9408b4b4626a52d7175743.tar.bz2 | |
Merge #21739: mention subtle difference between loops and listcomps in tutorial.
| -rw-r--r-- | Doc/tutorial/datastructures.rst | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/Doc/tutorial/datastructures.rst b/Doc/tutorial/datastructures.rst index 5e95afa..6dc17aa 100644 --- a/Doc/tutorial/datastructures.rst +++ b/Doc/tutorial/datastructures.rst @@ -200,12 +200,17 @@ For example, assume we want to create a list of squares, like:: >>> squares [0, 1, 4, 9, 16, 25, 36, 49, 64, 81] -We can obtain the same result with:: +Note that this creates (or overwrites) a variable named ``x`` that still exists +after the loop completes. We can calculate the list of squares without any +side effects using:: + + squares = list(map(lambda x: x**2, range(10))) + +or, equivalently:: squares = [x**2 for x in range(10)] -This is also equivalent to ``squares = list(map(lambda x: x**2, range(10)))``, -but it's more concise and readable. +which is more concise and readable. A list comprehension consists of brackets containing an expression followed by a :keyword:`for` clause, then zero or more :keyword:`for` or :keyword:`if` |