Python – How to extract from a list of objects a list of specific attribute

python

I have a list of objects. Object has 3 string attributes. I want to make a list containing only a specific attribute from class.

Is there any built-in functions to do that?

Best Solution

A list comprehension would work just fine:

[o.my_attr for o in my_list]

But there is a combination of built-in functions, since you ask :-)

from operator import attrgetter
map(attrgetter('my_attr'), my_list)

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Python – How to check if a list is empty

if not a:
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Using the implicit booleanness of the empty list is quite pythonic.

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Use the subprocess module in the standard library:

import subprocess
subprocess.run(["ls", "-l"])

The advantage of subprocess.run over os.system is that it is more flexible (you can get the stdout, stderr, the "real" status code, better error handling, etc...).

Even the documentation for os.system recommends using subprocess instead:

The subprocess module provides more powerful facilities for spawning new processes and retrieving their results; using that module is preferable to using this function. See the Replacing Older Functions with the subprocess Module section in the subprocess documentation for some helpful recipes.

On Python 3.4 and earlier, use subprocess.call instead of .run:

subprocess.call(["ls", "-l"])

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