I have a list of strings.
If one of the strings (e.g. at index 5) is the empty string, I want to replace it with "N".
How do I do that? The naive method (for a java programmer) does not work:
string_list[5] = "N"
gives
'str' object does not support item assignment
(string_list originally came from a .csv-file- that is why it might contain empty strings.)
Your error seems to indicate that your string_list is not a list of string but a real string (that doesn't support assignement because a string is immutable).
If your string_list was a real list of strings, like this for example : string_list = ["first", "second", "", "fourth"], then you will be able to do string_list[2] = "third" to obtain string_list = ["first", "second", "third", "fourth"].
If you need to automatically detect where an empty string is located in your list, try with index :
string_list[string_list.index("")] = "replacement string"
print string_list
>>> ["first", "second", "replacement string", "fourth"]
You say you have a list of strings but from you error it looks like you're trying to index a string
l = ["a", "b", "", "c"]
Is a list of strings.
l = ["N" if not x else x for x in l]
Is a list of strings with empty strings replaced with "N"
Try this:
>>> s = 'abc de'
>>> s.replace(' ', 'N')
'abcNde'
As mentioned by the others, it sounds like string_list is actually a string itself, meaning that you can't use assignment to change a character.
In python work with lists and convert them to strings when need be.
>> str = list("Hellp")
>> str
['H', 'e', 'l', 'l', 'p']
>> str[4] = 'o'
>> str
['H', 'e', 'l', 'l', 'o']
TO make it a string use
>> "".join(str)
'Hello World'
Python strings are immutable and they cannot be modified.
Or you could use List Comprehensions.
Some thing like:
>> myStr = ['how', 'are', 'yew', '?']
>> myStr = [w.replace('yew', 'you') for w in myStr]
The following example iterates through lists of lists (sublists), in order to replace a string, a word:
myoldlist=[['aa bbbbb'],['dd myword'],['aa myword']]
mynewlist=[]
for i in xrange(0,3,1):
mynewlist.append([x.replace('myword', 'new_word') for x in myoldlist[i]])
print mynewlist
# ['aa bbbbb'],['dd new_word'],['aa new_word']
string_listis actually a string, not a list of strings. Lists are mutable, so you should be able to replace its item just like you did.string_list?