finding and replacing elements in a list

python list replace
James picture James · Apr 6, 2010 · Viewed 977.4k times · Source

I have to search through a list and replace all occurrences of one element with another. So far my attempts in code are getting me nowhere, what is the best way to do this?

For example, suppose my list has the following integers

>>> a = [1,2,3,4,5,1,2,3,4,5,1]

and I need to replace all occurrences of the number 1 with the value 10 so the output I need is 

>>> a = [10, 2, 3, 4, 5, 10, 2, 3, 4, 5, 10]

Thus my goal is to replace all instances of the number 1 with the number 10.

Answer

outis picture outis · Apr 6, 2010

Try using a list comprehension and the ternary operator.

>>> a=[1,2,3,1,3,2,1,1]
>>> [4 if x==1 else x for x in a]
[4, 2, 3, 4, 3, 2, 4, 4]

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