removing unwanted characters from a string

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May 7th, 2004, 02:00 PM

lblack750

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removing unwanted characters from a string

I was wondering how to remove a character from a string that was retreived from a text file (.txt).

May 7th, 2004, 02:37 PM

DevCoach

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If you only want to remove all instances of a single character, then you can use the string replace method:

Code:

>>> txt = 'hello world'
>>> txt.replace('l', '')
'heo word'

To remove a set of characters then you could use the filter function:

Code:

>>> filter(lambda x: x not in 'aeiou', txt)
'hll wrld'

Alternatively you could use the string module's translate and maketrans functions:

Code:

>>> import string
>>> trans = string.maketrans('', '')
>>> string.translate(txt, trans, 'aeiou')
'hll wrld'

The translate function is more useful if you wish to replace some characters and remove others.
EDIT: translate is also much faster than filter, since it is implemented entirely in C, while filter will need to call a python function for each character. This probably does not matter much for scripts occasionally acting on short strings, but can be critical if performance is an issue.

Dave - The Developers' Coach

Last edited by DevCoach : May 8th, 2004 at 06:04 PM.

May 8th, 2004, 04:06 PM

sfb

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It all depends which characters you want to remove...

To remove whitespace characters (space, tabs, newlines, etc) from the left end of the string:

Code:

>>> txt = "  Hello World  "
>>> txt.lstrip()
"Hello World  "

From the right of the string:

Code:

>>> txt = "  Hello World  "
>>> txt.rstrip()
"  Hello World"

From both sides:

Code:

>>> txt = "  Hello World  "
>>> txt.strip()
"Hello World"

To remove the first character:

Code:

>>> txt = "Hello World"
>>> txt[1:]
"ello World"

The last character:

Code:

>>> txt = "Hello World"
>>> txt[:-1]
"Hello Worl"

The 5th character (or the nth character(s)):

Code:

>>> txt = "Hello World"
>>> txt[:5] + t[6:]
"HelloWorld"

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