Separating specific portion of a string in python

Question

I am sending information via SCPI to power supplies. I created a GUI to display its responses. One of the responses comes is an error message that is a string and it has a character, a number, a comma and a couple of words in quotation marks. Ex: +0,"No Error" I need to extract just what is in the quotation marks, so what would be displayed is No Error. I was trying to split it and then truncate it from the quotation mark, however it is never as clean as I need and I can't cut the string by simply doing _mystring[4:-1] because some of the error codes being sent back are different lengths. ie. -400,"Query Error"

So doing _mystring[4:-1] would display ","Query Error"

help

You should look into regular expressions https://www.w3schools.com/python/python_regex.asp — C_Z_, Jun 28 '22 at 18:49
You should include your attempts at splitting. Did you try splitting on comma then splitting on `"`? — wwii, Jun 28 '22 at 18:51
Have you checked the docs for the [str.split()](https://docs.python.org/3.3/library/stdtypes.html?highlight=split#str.split) method? — G. Anderson, Jun 28 '22 at 18:52

S3DEV · Answer 1 · 2022-06-28T18:59:20.450

Regular expressions via the built-in re library are used to extract portions of strings, matching a given pattern.

Pattern explanation: '\"(.*)\"'

Find a quotation mark
Capture any number of characters until another quotation mark is found
As the .findall() method returns all matches, (zero, one or more) the [0] index and simply returns the first match.

Documentation for the .findall() method is linked here.

Example code:

import re

string = '+0,"No Error"'
re.findall('\"(.*)\"', string)[0]

Output:

'No Error'

Iterative test:

str1 = '+0,"No Error"'
str2 = '-400,"Query Error"'
rexp = re.compile('\"(.*)\"')

for string in [str1, str2]:
    print(rexp.findall(string)[0])

Output:

No Error
Query Error

score 0 · Answer 2 · answered Jun 28 '22 at 18:53

0

A rudimental approach using string split-method:

response = '+0,"No Error"'

msg = response.split('"')[1]

print(msg)
#No Error

For a more robust solution consider to use a regular expression.

answered Jun 28 '22 at 18:53

cards

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This is perfect, I was trying to mess with split earlier but wasn't getting the results I wanted, I understand what I was missing now – Joshua Reck Jun 28 '22 at 20:09
@Joshua Reck since the string contains two quotes the split generates three terms and you need the one in the middle – cards Jun 28 '22 at 20:18

Dima Chubarov · Answer 3 · 2022-06-28T19:02:03.820

Consider using regular expressions

import re

message = '-400,"Query Error"'
pattern = '(.)([0-9]+),"([^"]*)"'
result = re.match(pattern, message)

symbol = result.group(1)
code = int(result.group(2))
text = result.group(3)

print(f'symbol: {symbol}\ncode: {code}\ntext: {text}')

Here pattern defines 3 groups indicated by brackets.

First group contains a single character, as . matches any character.
Second group contains a sequence of one or more digits
Third group contains any number of characters other than a quotation mark in quotes. Quotes are excluded from the group.

Separating specific portion of a string in python

3 Answers3