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I want to write a code that replaces a certain string '-1' with '0' on the list. But I'm having a hard time writing if statements.

list = [-1, 1, -1]
if '-1' in list:
   code that replace -1 to 0   <--- What I want to add
else:
   pass

What I tried to do was the code below.

if i in list:
    temp = i.replace("-1","0")
    list.append(temp)
    print(list)
else:
    pass

But this code shows "NameError: name 'i' is not defined".

Emma Lim
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  • Does this answer your question? [finding and replacing elements in a list](https://stackoverflow.com/questions/2582138/finding-and-replacing-elements-in-a-list) – jizhihaoSAMA Jul 05 '21 at 04:02

3 Answers3

3

You can use list-comprehension and take 0 if list item is -1 else just take the list item. Also as a side note, don't use list for variable name:

>>> [0 if i==-1 else i for i in List]
[0, 1, 0]
ThePyGuy
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1

You can use enumerate and replace with index

list2 = [-1, 1, -1]
for i,j in enumerate(list2):
    if j==-1:
       list2[i]=0
print(list2)
1

One thing you seem to be doing is mixing integers with strings: Your list contains integers: list = [-1, 1, -1] but you are trying to compare strings: temp = i.replace("-1","0")

Here is an example of replacing a list of integers and a list of strings:

list a is integers and list b is strings:

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

for i in range(0,len(a)):
    print(a[i])
    if(a[i]==-1):
        print("replace")
        a[i]=0
print(a)

b= ["1", "2", "3", "4", "-1", "1", "2", "-1", "4", "5", "1"]

for i in range(0,len(b)):
    print(b[i])
    if(b[i]=="-1"):
        print("replace")
        b[i]="0"
print(b)
jester
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