in Python how to increment the values in a list without having to write a for loop, e.g.:
group = [0]*3
item = [1,2,3]
group += item
print group
to get group = [1,2,3] instead of group = [0,0,0,1,2,3] ?
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Why increment? Why not copy the item into group?Malik Brahimi– Malik Brahimi2015-02-23 13:05:47 +00:00Commented Feb 23, 2015 at 13:05
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Something like this might be helpful: stackoverflow.com/q/263457/1558022alexwlchan– alexwlchan2015-02-23 13:06:36 +00:00Commented Feb 23, 2015 at 13:06
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stackoverflow.com/questions/14050824/…Tim– Tim2015-02-23 13:06:59 +00:00Commented Feb 23, 2015 at 13:06
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2 Answers
You could use numpy module. This won't need a for loop.
>>> import numpy as np
>>> group = np.array([0]*3)
>>> item = np.array([1,2,3])
>>> group += item
>>> group
array([1, 2, 3])
>>> list(group)
[1, 2, 3]
Comments
You can do element-wise operations (addition in this case) by using zip within a list comprehension.
>>> group = [0]*3
>>> item = [1,2,3]
>>> group = [i + j for i,j in zip(group, item)]
>>> group
[1, 2, 3]
This is a general solution if group didn't start out as all zeroes, and you wanted to add the current values with some new values.
