assign value multiple times array, python

Question

I have a list of elements in Python and need to assign a number to the entire list. In R, I could simply do the assignment and R would rep that number the necessary number of times. In Python, is the easiest thing to do a list comprehension?

x = [1,2,3,4,5]
#want to assign 0 to every element, would like to do x[:] = 0 but this causes an error
x[:] = [0 for i in range(len(x))] #pretty long for such a simple operation

What's the difference between "assigning 0 to the entire list" and "making a new list of 0s the same length"? — TessellatingHeckler, Jan 09 '16 at 02:42

score 2 · Accepted Answer · answered Jan 09 '16 at 02:41

Yes, a comprehension such as [0 for _ in x] is the way to go (no need for range(len(... if you're not doing anything with the values). R's syntax places heavy emphasis on vectors, while Python has a preference for explicit instructions in this sort of case.

score 1 · Answer 2 · answered Jan 09 '16 at 02:42

1

You could also try:

x = [1,2,3,4,5]
x = [0] * len(x)

Hope this helps.

answered Jan 09 '16 at 02:42

station

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score 1 · Answer 3 · answered Jan 09 '16 at 02:42

1

>>> x[:] = [0]*len(x)
>>> x
[0, 0, 0, 0, 0]

answered Jan 09 '16 at 02:42

mechanical_meat

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using the multiplication operator can be dangerous on mutable objects. Probably worth mentioning... – Reut Sharabani Jan 09 '16 at 02:46

assign value multiple times array, python

3 Answers3