如何在 python 中替换字符串开头和结尾的字符

Question

I have a string:

path = "{'ResponseMetadata': {'Flag': 'Processed', 'Message': 'File Ingested successfully', 'INGEST_PATH': ['inward/emr_batch/manual_cars/xy99', ""manual_cars/xy99/2020/08/12/145938/ABC KPI's Jan 2018.csv""]}}

I would like to replace ' at the beginning and end of the strings only and not in middle of strings.

I am trying to make use of replace function of python to perform this task

path = path.replace("\'", "\"")

but above approach is replacing the ' every where in string and output obtained is

{"ResponseMetadata": {"Flag": "Processed", "Message": "File Ingested successfully", "INGEST_PATH": ["inward/emr_batch/manual_cars/xy99", ""manual_cars/xy99/2020/08/12/145938/ABC KPI"s Jan 2018.csv""]}}

but I do not want KPI's to get change to KPI"s, one way which i can achieve this is to make use of replace function again like below to gain desired output , but then problem with below approch is that I need to keep on adding replace with each new scenario and I would like to have generic solution can some one help here.

path = path.replace("\'", "\"").replace('"s', "'s")

Regards Mahi

Answer 1

First, your string is invalid. So i'm defining it with triple quotes:

path = """{'ResponseMetadata': {'Flag': 'Processed', 'Message': 'File Ingested successfully', 'INGEST_PATH': ['inward/emr_batch/manual_cars/xy99', ""manual_cars/xy99/2020/08/12/145938/ABC KPI's Jan 2018.csv""]}}"""

How about iterating over the string's characters and checking the surrounding characters for isalpha() :

out = []
for ix, char in enumerate(path):
  # first make sure we have a surrounding character on each side
  if ix > 0 and ix < len(path):
    # now check for a quote and make sure that one of the surrounding characters are not letters
    if char == "'" and not (path[ix-1].isalpha() and path[ix+1].isalpha()):
      # if we find that case, replace the single quote
      char = '"'
  # add the character to the out list
  out.append(char)

# join all the characters back together
output = ''.join(out)

print(output)

Result (again, this is invalid to paste directly, unless it is triple quoted):

{"ResponseMetadata": {"Flag": "Processed", "Message": "File Ingested successfully", "INGEST_PATH": ["inward/emr_batch/manual_cars/xy99", ""manual_cars/xy99/2020/08/12/145938/ABC KPI's Jan 2018.csv""]}}

Answer 2

Here is simple attempt you can simply replace all and thereafter replace back the double quotes followed by letter s like the following

import re

path = '''
{'ResponseMetadata': {'Flag': 'Processed', 'Message': 'File Ingested successfully', 'INGEST_PATH': ['inward/emr_batch/manual_cars/xy99', ""manual_cars/xy99/2020/08/12/145938/ABC KPI's Jan 2018.csv""]}}
'''

path_ = re.sub('\'', '\"', path)
print(re.sub('\"s','\'s', path_))

output

{"ResponseMetadata": {"Flag": "Processed", "Message": "File Ingested successfully", "INGEST_PATH": ["inward/emr_batch/manual_cars/xy99", ""manual_cars/xy99/2020/08/12/145938/ABC KPI's Jan 2018.csv""]}}

you can target everywhere you want to replace like

print(re.sub('KPI\"','KPI\'', path_))

Answer 3

I would recommend regular expressions.

https://en.m.wikibooks.org/wiki/Python_Programming/Regular_Expression

https://docs.python.org/3/library/re.html

second link shows the regular expression language.

import re
path = """{'ResponseMetadata': {'Flag': 'Processed', 'Message': 'File Ingested successfully', 'INGEST_PATH': ['inward/emr_batch/manual_cars/xy99', ""manual_cars/xy99/2020/08/12/145938/ABC KPI's Jan 2018.csv""]}}"""

m=re.sub(r"'([^']*)'",r'"\1"',path)

print(m)

sub has the following signature: re.sub(pattern, repl, string, count=0, flags=0)

1. "([^']*)" <== this is a group, because of () and accepts all signs except '
2. '"\1"' <== this is the replacer and will replace all founds with "(group)"

result: {"ResponseMetadata": {"Flag": "Processed", "Message": "File Ingested successfully", "INGEST_PATH": ["inward/emr_batch/manual_cars/xy99", ""manual_cars/xy99/2020/08/12/145938/ABC KPI's Jan 2018.csv""]}}

Best regards