Changing a character in a string

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October 27th, 2012, 07:32 PM

Dzung

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Changing a character in a string

Hi,

How would you change a character in a string.

from: string = "cat"

to: string = "cot"

thanks

October 27th, 2012, 07:52 PM

b49P23TIvg

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I'd convert the string to a list, make the changes, then convert back to a string.

Code:

>>> s = list('cat')
>>> s
['c', 'a', 't']
>>> s[1] = 'o'
>>> ''.join(s)
'cot'
>>>

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October 27th, 2012, 10:13 PM

Lux Perpetua

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Quote:

Originally Posted by Dzung

Hi,

How would you change a character in a string.

from: string = "cat"

to: string = "cot"

thanks

To elaborate on b's reply, you technically can't do what you posted, since strings in Python are immutable: they cannot be "changed." However, lists are mutable, so you can take a sting apart into a list, change the list, and put it back together into a different string. You can even use the old variable name (`string' in your example) to refer to the new string, so it's essentially as if you had changed the string. (But not completely: if there were other references to the original string in your program, they will still refer to the old string.)

October 29th, 2012, 10:45 PM

spiralbrain

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Quote:

Originally Posted by b49P23TIvg

I'd convert the string to a list, make the changes, then convert back to a string.

Code:

>>> s = list('cat')
>>> s
['c', 'a', 't']
>>> s[1] = 'o'
>>> ''.join(s)
'cot'
>>>

In your example, why is ''.join(s), even needed? Or I should say what is the purpose of adding it?

thanks!

October 30th, 2012, 02:29 AM

Lux Perpetua

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Quote:

Originally Posted by spiralbrain

In your example, why is ''.join(s), even needed? Or I should say what is the purpose of adding it?

thanks!

['c', 'o', 't'] is a list. ''.join(['c', 'o', 't']) is a string. This is the third part of the procedure I stated in my post (putting the list back together into a string).

October 30th, 2012, 03:47 PM

spiralbrain

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Quote:

Originally Posted by Lux Perpetua

['c', 'o', 't'] is a list. ''.join(['c', 'o', 't']) is a string. This is the third part of the procedure I stated in my post (putting the list back together into a string).

Got it.

Changing a character in a string

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