Trying to convert Sed command to Python re.sub

Question

I am trying to convert the below Sed command to python re.sub. The Sed command is basically extracting the access_token value from the json string.

finalString=$(echo $initialString |  sed -e 's/^.*"access_token":"\([^"]*\)".*$/\1/')

My Python code, I was stuck in replacing the \\1 part. I have to replace the whole string with the value

access_token = re.sub('^.*"access_token":"\([^"]*\)".*$',r'\1',initialString)
print access_token

My working echo statement is as follows, When I run this I am getting the access_token value. For Ex: If initialString ='{"access_token":"xyz"}' output will be xyz .

echo initialString | sed -e 's/^.*"access_token":"\([^"]*\)".*$/\1/'

Answer 1

In general, you should make it a rule to always use raw-strings as regular expressions in Python. (In specific, it doesn't matter here. But it's a good rule of thumb.)

Try this:

access_token = re.sub(r'^.*"access_token":"([^"]*)".*$', r'\1', initialString)

Answer 2

I'm working on the assumption that your intialString is something along the lines of: "other":"json","access_token":"(1234)","more":"json"

access_token = re.sub(r'^.*"access_token":"\(([^\)]*)\)".*$',r'\1',initialString)

The problem I noticed was that you were never actually capturing any characters to reference with \\1.