Python- how to replace characters in a list item in a list

Question

I am a beginner in python and am trying to tackle this problem and just cannot get my output right. I am trying to change the value of an item in a list and pass the item to a new list.

mylist = []
test = ['path', 'name', 'user1', 'orig']
for i in test:
     if 'user' in i:
          mylist = 'user' # or i[:-1]
     else:
          mylist = i
mylist

any help would be appreciated or point me to the answer

Damon

a list ['path', 'name', 'user', 'orig'] essentially changing the list item 'user1' and removing the last character but keeping the other items in the list — Damonv2, Dec 19 '18 at 15:37

score 1 · Answer 1 · answered Dec 19 '18 at 15:39

1

You can do a list-comprehension:

test = ['path', 'name', 'user1', 'orig']

mylist = ['user' if 'user' in x else x for x in test]
# ['path', 'name', 'user', 'orig']

answered Dec 19 '18 at 15:39

Austin

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this is a really good example/explaniation of [list comprehensions](https://www.pythonforbeginners.com/basics/list-comprehensions-in-python) – chitown88 Dec 19 '18 at 15:49

yatu · Answer 2 · 2018-12-19T15:45:12.633

1

Note that when you do:

`mylist = 'user'`

You are replacing whatever there was in that list with 'user'. So instead you want to specify an index, say mylist[i] = 'user', or use append.

This however can be simplified using a list comprehension:

[i if 'user' not in i else 'user' for i in l ]
['path', 'name', 'user', 'orig']

edited Dec 19 '18 at 15:45

answered Dec 19 '18 at 15:40

yatu

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score 0 · Accepted Answer · answered Dec 19 '18 at 15:38

Looks like this is what you want: append

>>> mylist = []
>>> test = ['path', 'name', 'user1', 'orig']
>>> for i in test:
...      if 'user' in i:
...           mylist.append(i[:-1])
...      else:
...           mylist.append(i)
...
>>> mylist
['path', 'name', 'user', 'orig']

chitown88 · Answer 4 · 2018-12-19T15:50:38.737

0

list comprehension probably the best answer. but since you're learnng, it's good to see the expanded way too.

mylist = []
test = ['path', 'name', 'user1', 'orig']
for x in test:
    if 'user' in x:
        x = 'user'  
        mylist.append(x)
    else:
        mylist.append(x)
mylist

edited Dec 19 '18 at 15:50

answered Dec 19 '18 at 15:42

chitown88

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score 0 · Answer 5 · answered Dec 19 '18 at 15:43

Since you're learning, I propose a solution as similar as possible to your approach:

mylist = []
test = ['path', 'name', 'user1', 'orig']
for i in test:
     if 'user' in i:
          mylist.append('user') # or i[:-1]
     else:
          mylist.append(i)

print(mylist)

As you can see, I added the method .append(), list method that allows you to insert an element at the end of a list.

What you were doing, with the = sign, was an assignment: the value of mylist was reassigned each time.

In this QA you can find an explanation on how to use .append(), or you can have a look at the official documentation

Python- how to replace characters in a list item in a list

5 Answers5