I have a few lists that I want filtered. Consider the following example:
a = [1,2]
b = [2,3]
l = [a,b]
for i in l:
i = [elem for elem in l if elem != 2]
I want the output to be a==[1]
, b==[3]
, but it looks like the update of i
does not change the elements a
or b
. In C , I'd use a pointer but I can't seem to find the corresponding concept in Python.
CodePudding user response:
By assigning to i
a new list in your for
loop, it loses its reference to a
and b
so they do not get updated. Instead, you should update i
in-place. You should also iterate through i
instead of l
to filter each sub-list:
for i in l:
i[:] = (elem for elem in i if elem != 2)
Demo: https://replit.com/@blhsing/BlissfulWhichGravity
CodePudding user response:
Are you certain you don't just want something like the following?
a = [1, 2]
b = [2, 3]
l = [[i for i in a if i != 2], [i for i in b if i != 2]]
Or perhaps more flexibly:
exclude = (2,)
a = [1, 2]
b = [2, 3]
l = [a, b]
l = [[i for i in x if not any(i == e for e in exclude)] for x in l]
This latter approach makes it each to add additional sublists to l
, and to specify more numbers to exclude from them.
CodePudding user response:
Try this:
a = [1,2]
b = [2,3]
l = [a,b]
for i in l:
i.remove(2)
print(a)
print(b)
print(l)
Output:
[1]
[3]
[[1], [3]]