Python Regex for pattern matching

Question

I am trying to parse the sample input test_string1 as below:

import re
TEST_STRING1 = """Using definitions from (yyyy/mm/dd): 2016/6/8
The following files are collected:
  File: Test.exe
    Source: Google
    avping blob: 123123

Downloaded 3 Files
"""
def fun():

    regex_exp = re.compile(r"File:\s(?P<File>[^\n\r\t]+?)[\n\r\t\s]*?"
                           r"Source:\s(?P<Source>.*)[^\w\d]*?"
                           r"avping\sblob:\s(?P<Avping_blob>([A-F]|[a-f]|[0-9]){6})")
    result = {}
    result['Files'] = []
    for m in re.finditer(regex_exp, TEST_STRING1):
        result['Files'].append(m.groupdict())
    print result
if __name__ == "__main__":
    fun()

Output of the Above code is :

{'Files': [{'Source': 'Google', 'File': 'Test.exe', 'Avping_blob': '123123'}]}

I want to make some fields in Input optional such as avping blob: Like

TET_STRING1 = """Using definitions from (yyyy/mm/dd): 2016/6/8
The following files are collected:
  File: Test.exe
    Source: Google

Downloaded 3 Files
"""

In that casa above regex return no match.

I have updated the regex as

regex_exp = re.compile(r"(File:\s(?P<File>[^\n\r\t]+?)[\n\r\t\s]*?"
                           r"Source:\s(?P<Source>.*)[^\w\d]*?"
                           r"|avping\sblob:\s(?P<Avping_blob>([A-F]|[a-f]|[0-9]){6}))")

by adding | before last line. But then It gives 2 matches with OR as

{'Files': [{'Source': 'Google', 'File': 'Test.exe', 'Avping_blob': None}, {'Source': None, 'File': None, 'Avping_blob': '123123'}]}

How should I write regex that will match the pattern for both input types (with and without optional fields)? Thanks

Wiktor Stribiżew · Accepted Answer · 2016-06-15 10:38:20Z

1

You may use an optional non-capturing group and use [^\w\d]* greedy version:

(File:\s(?P<File>[^\n\r\t]+?)[\n\r\t\s]*?Source:\s(?P<Source>.*)[^\w\d]*(?:avping\sblob:\s(?P<Avping_blob>[A-Fa-f0-9]{6}))?)

See the regex demo

In your code:

regex_exp = re.compile(r"(File:\s(?P<File>[^\n\r\t]+?)[\n\r\t\s]*?"
                       r"Source:\s(?P<Source>.*)[^\w\d]*"    # <- Here ? is removed
                       r"(?:avping\sblob:\s(?P<Avping_blob>[A-Fa-f0-9]{6}))?)")
                         ^^^                                               ^

Also, ([A-F]|[a-f]|[0-9]){6}) = (?P<Avping_blob>[A-Fa-f0-9]{6}).

edited Jun 15, 2016 at 10:38

answered Jun 15, 2016 at 10:28

Wiktor Stribiżew

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2 Comments

ajay_t Over a year ago

Thanks for your answer: I am getting result as '{'Files': [{'Source': 'Google', 'File': 'Test.exe', 'Avping_blob': None}]}' in both the cases in python code. avping_blob is NONE in both the cases

Wiktor Stribiżew Over a year ago

Try the updated version. So, the second one can be NONE, right?

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