Hidden features of Python

Questions

What are the lesser-known but useful features of the Python programming language?

• Try to limit answers to Python core.
• One feature per answer.
• Give an example and short description of the feature, not just a link to documentation.
• Label the feature using a title as the first line.

Quick links to answers:

http://stackoverflow.com/questions/101268/hidden-features-of-python#111176 http://stackoverflow.com/questions/101268/hidden-features-of-python#111176 http://stackoverflow.com/questions/101268/hidden-features-of-python#112303 http://stackoverflow.com/questions/101268/hidden-features-of-python#112303 http://stackoverflow.com/questions/101268/hidden-features-of-python#101945 http://stackoverflow.com/questions/101268/hidden-features-of-python#101945 http://stackoverflow.com/questions/101268/hidden-features-of-python#101447 http://stackoverflow.com/questions/101268/hidden-features-of-python#101447 http://stackoverflow.com/questions/101268/hidden-features-of-python#113198 http://stackoverflow.com/questions/101268/hidden-features-of-python#113198 http://stackoverflow.com/questions/101268/hidden-features-of-python#102062 http://stackoverflow.com/questions/101268/hidden-features-of-python#102062 http://stackoverflow.com/questions/101268/hidden-features-of-python#111970 http://stackoverflow.com/questions/101268/hidden-features-of-python#111970 http://stackoverflow.com/questions/101268/hidden-features-of-python#102065 http://stackoverflow.com/questions/101268/hidden-features-of-python#102065 http://stackoverflow.com/questions/101268/hidden-features-of-python/112316#112316 http://stackoverflow.com/questions/101268/hidden-features-of-python/112316#112316 http://stackoverflow.com/questions/101268/hidden-features-of-python#117116 http://stackoverflow.com/questions/101268/hidden-features-of-python#117116 http://stackoverflow.com/questions/101268/hidden-features-of-python#114420 http://stackoverflow.com/questions/101268/hidden-features-of-python#114420 http://stackoverflow.com/questions/101268/hidden-features-of-python#102202 http://stackoverflow.com/questions/101268/hidden-features-of-python#102202 http://stackoverflow.com/questions/101268/hidden-features-of-python#101310 http://stackoverflow.com/questions/101268/hidden-features-of-python#101310 http://stackoverflow.com/questions/101268/hidden-features-of-python#101276 http://stackoverflow.com/questions/101268/hidden-features-of-python#101276 http://stackoverflow.com/questions/101268/hidden-features-of-python#102037 http://stackoverflow.com/questions/101268/hidden-features-of-python#102037 http://stackoverflow.com/questions/101268/hidden-features-of-python#101840 http://stackoverflow.com/questions/101268/hidden-features-of-python#101840 http://stackoverflow.com/questions/101268/hidden-features-of-python#112286 http://stackoverflow.com/questions/101268/hidden-features-of-python#112286 http://stackoverflow.com/questions/101268/hidden-features-of-python#101537 http://stackoverflow.com/questions/101268/hidden-features-of-python#101537 http://stackoverflow.com/questions/101268/hidden-features-of-python#113164 http://stackoverflow.com/questions/101268/hidden-features-of-python#113164 http://stackoverflow.com/questions/101268/hidden-features-of-python#101549 http://stackoverflow.com/questions/101268/hidden-features-of-python#101549 http://stackoverflow.com/questions/101268/hidden-features-of-python#108297 http://stackoverflow.com/questions/101268/hidden-features-of-python#108297 http://stackoverflow.com/questions/101268/hidden-features-of-python#113833 http://stackoverflow.com/questions/101268/hidden-features-of-python#113833 http://stackoverflow.com/questions/101268/hidden-features-of-python#1024693 http://stackoverflow.com/questions/101268/hidden-features-of-python#1024693 http://stackoverflow.com/questions/101268/hidden-features-of-python#143636 http://stackoverflow.com/questions/101268/hidden-features-of-python#143636 http://stackoverflow.com/questions/101268/hidden-features-of-python#101739 http://stackoverflow.com/questions/101268/hidden-features-of-python#101739 http://stackoverflow.com/questions/101268/hidden-features-of-python#168270 http://stackoverflow.com/questions/101268/hidden-features-of-python#168270 http://stackoverflow.com/questions/101268/hidden-features-of-python#116480 http://stackoverflow.com/questions/101268/hidden-features-of-python#116480 http://stackoverflow.com/questions/101268/hidden-features-of-python#114157 http://stackoverflow.com/questions/101268/hidden-features-of-python#114157 http://stackoverflow.com/questions/101268/hidden-features-of-python#3267903 http://stackoverflow.com/questions/101268/hidden-features-of-python#3267903 http://stackoverflow.com/questions/101268/hidden-features-of-python#109182 http://stackoverflow.com/questions/101268/hidden-features-of-python#109182

Answers

Chaining comparison operators:

>>> x = 5
>>> 1 < x < 10
True
>>> 10 < x < 20 
False
>>> x < 10 < x*10 < 100
True
>>> 10 > x <= 9
True
>>> 5 == x > 4
True

In case you re thinking it s doing 1 < x, which comes out as True, and then comparing True < 10, which is also True, then no, that s really not what happens (see the last example.) It s really translating into 1 < x and x < 10, and x < 10 and 10 < x * 10 and x*10 < 100, but with less typing and each term is only evaluated once.

Source

License : cc by-sa 3.0

http://stackoverflow.com/questions/101268/hidden-features-of-python

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