Is it possible to replace elements of a list with a "for in" iteration in Python?-CodePudding

I'm trying to iterate over a list and change its values with a "for in" loop:

example_string = "This is a string."

for char in example_string :
    char = 'r'

example_list = list(example_string)

for char in example_list:
    char = 'r'

The string object is not modified by the iteration.

Does the "for in" iteration in Python returns another variable and not the actual list/string element?

I tried doing it with lists. I expected that the items in the list or string would get changed by the assignment.

CodePudding user response：

You can change in a list, but use the index instead:

example_string = ["This is a string.", "This is another string"]

for i in range(len(example_string)):
    example_string[i] = "r"

print(example_string)

In your example, only the variable would change:

example_string = "This is a string."

for char in example_string:
    char = 'r'
    print(char)

You can select from your string using the index as well, however the string itself is immutable and you can't reassign directly in it:

Textual data in Python is handled with str objects, or strings. Strings are immutable sequences of Unicode code points.

CodePudding user response：

Yes its definitely possible with a for loop but you are not changing the original variable: example_string in your code. Try creating a new list and append or insert the new value in every iteration.

CodePudding user response：

Try defining a function in which you create a new list (or string) and append the changed elements in your for-in loop. An example of what I mean:

def change_in_list(_list):
  new_list = []
  for element in _list:
    element = 'CHANGED'
    new_list.append(element)
  return new_list

example_list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
print(example_list)
print(change_in_list(example_list))

output from list

For a string you would use

def modify_string(_string):
  new_string = ''
  for character in _string:
    character = 'CHANGED'
    new_string  = character
  return new_string

example_string = 'Hello World'
print(example_string)
print(modify_string(example_string))

The output here is string output

Both can be modified/adapted to your needs but I hope this helps