如何在python中替换列表中的单引号

Question

I have a list:

my_list = ['"3"', '"45"','"12"','"6"']

This list has single and double quotes and the item value. How can I replace either the single or double quotes from each item. I tried below, but the results are same:

my_list = [i.replace("''", " ") for i in my_list]

Answer 1

Your list doesn't contain any strings with single quotes. I think you are confusing the repr() representation of the strings with their values.

When you print a Python standard library container such as a list (or a tuple, set, dictionary, etc.) then the contents of such a container are shown their repr() representation output; this is great when debugging because it makes it clear what type of objects you have. For strings, the representation uses valid Python string literal syntax; you can copy the output and paste it into another Python script or the interactive interpreter and you'll get the exact same value.

For example, s here is a string that contains some text, some quote characters, and a newline character. When I print the string, the newline character causes an extra blank line to be printed, but when I use repr() , you get the string value in Python syntax form, where the single quotes are part of the syntax , not the value. Note that the newline character also is shown with the \\n syntax, exactly the same as when I created the s string in the first place:

>>> s = 'They heard him say "Hello world!".\n'
>>> print(s)
They heard him say "Hello world!".

>>> print(repr(s))
'They heard him say "Hello world!".\n'
>>> s
'They heard him say "Hello world!".\n'

And when I echoed the s value at the end, the interactive interpreter also shows me the value using the repr() output.

So in your list, your strings do not have the ' characters as part of the value. They are part of the string syntax. You only need to replace the " characters, they are part of the value, because they are inside the outermost '...' string literal syntax. You could use str.replace('"', '') to remove them:

[value.replace('"', '') for value in my_list]

or, you could use the str.strip() method to only remove quotes that are at the start or end of the value:

[value.strip('"') for value in my_list]

Both work just fine for your sample list:

>>> my_list = ['"3"', '"45"','"12"','"6"']
>>> [value.replace('"', '') for value in my_list]
['3', '45', '12', '6']
>>> [value.strip('"') for value in my_list]
['3', '45', '12', '6']

Again, the ' characters are not part of the value:

>>> first = my_list[0].strip('"')
>>> first         # echo, uses repr()
'3'
>>> print(first)  # printing, the actual value written out
3
>>> len(first)    # there is just a single character in the string
1

However , I have seen that you are reading your data from a tab-separated file that you hand-parse. You can avoid having to deal with the " quotes altogether if you instead used the csv.reader() object , configured to handle tabs as the delimiter. That class automatically will handle quoted columns:

import csv

with open(inputfile, 'r', newline='') as datafile:
    reader = csv.reader(datafile, delimiter='\t')
    for row in reader:
        # row is a list with strings, *but no quotes*
        # e.g. ['3', '45', '12', '6']

Demo showing how csv.reader() handles quotes:

>>> import csv
>>> lines = '''\
... "3"\t"45"\t"12"\t"6"
... "42"\t"81"\t"99"\t"11"
... '''.splitlines()
>>> reader = csv.reader(lines, delimiter='\t')
>>> for row in reader:
...     print(row)
...
['3', '45', '12', '6']
['42', '81', '99', '11']

Answer 2

As suggested by @MartijnPieters in comments, you can use replace on the strings to get the desired output.

The change I like to suggest is that using .replace('"', '') instead of .replace('"', ' ') . Otherwise the resultant strings will have a leading and trailing white space

You can use list comprehension to deal with the list you have like this

my_list = ['"3"', '"45"','"12"','"6"']

new_list = [x.replace('"', '') for x in my_list]

print(new_list) # ['3', '45', '12', '6']

Answer 3

You can use split:

[x.split('"')[1] for x in my_list]

or you can use:

[x.strip('"') for x in my_list]