python: how to replace a string in a list of string with a list of strings?

Question

okay here is the example:

data = ['This', 'is', 'a', 'test', 'of', 'the', 'list']
replaceText = 'test'
replaceData =['new', 'test']

i did data.replace(replaceText, replaceData) but it doesn't work. How to replace a string in a list of string with a list of strings? Any help will be appreciated.

Edit: The exact condition is to replace or split the words that contain "s" so I put a loop in it. So the end result will print data = ['Thi', 'i', 'a', 'te','t', 'of', 'the', 'li','t']

Answer 1

In a list, find the position of text with .index(), then replace by using slice assignment:

pos = data.index(replaceText)
data[pos:pos+1] = replaceData

This will replace only one occurrence of replaceText at a time. Demo:

>>> data = ['This', 'is', 'a', 'test', 'of', 'the', 'list']
>>> replaceText = 'test'
>>> replaceData =['new', 'test']
>>> pos = data.index(replaceText)
>>> data[pos:pos+1] = replaceData

To replace all occurences, use pos plus the length of replaceData to skip searching past the previous match:

pos = 0
while True:
 try:
 pos = data.index(replaceText, pos)
 except ValueError:
 break
 data[pos:pos+1] = replaceData
 pos += len(replaceData)

If you need to loop over data while modifying it, use a copy instead:

for n in data[:]:
 # maniplate data

• tipsywacky: actually the condition has made me to loop data. i posted the code above. would your method still work?
• Martijn Pieters: Your loop makes no sense. You cannot loop over data and change it in-place, for example. Do you mean that you'll replace multiple things at a time?
• tipsywacky: yah, the actually condition needs me to replace or split any string that contains the character 's', say 'test' will be replaced by 'te' and 't' to the list.
• tipsywacky: also "list" will be split in to "li" and "t" and replaced to the list.
• Jon Clements: @tipsywacky I've added an answer that does that (if I'm understanding correctly) - you may wish to update the question

Answer 2

You can use list's index() method to find the position p of replaceText:

p = data.index(replaceText)

and then use the construct

data[start:end] = another_list

to replace elements from p to p+1 (end is not inclusive) with replaceData:

data[p:p+1] = replaceData

Note that index() throws ValueError if replaceText does not exist in data:

try:
 p = data.index(replaceText)
 data[p:p+1] = replaceData
except ValueError:
 # replaceText is not present in data, handle appropriately.

Answer 3

yah, the actually condition needs me to replace or split any string that contains the character 's', say 'test' will be replaced by 'te' and 't' to the list

from itertools import chain
data = ['This', 'is', 'a', 'test', 'of', 'the', 'list']
>>> filter(None, chain.from_iterable(el.split('s') for el in data))
['Thi', 'i', 'a', 'te', 't', 'of', 'the', 'li', 't']