questions about Python regex
Why the following pattern string results in a match of "A cat", instead of "a hat" since match is greedy by default?
>>> m = re.match(r'(\w+) (\w+)', "A cat jumpped over a hat") >>> m <_sre.SRE_Match object; span=(0, 5), match='A cat'>
Could someone shed some light on them?
From official document:
If zero or more characters at the beginning of string match the regular expression pattern, return a corresponding match object. Return None if the string does not match the pattern; note that this is different from a zero-length match.
python-regex Archives, science and programming articles, quizzes and practice/competitive programming/company interview Questions. Regular Expression in Python with Examples | Set 1. The module re provides support for regular expressions in Python. Regular expression or Regex is a sequence of characters that is used to check if a string contains the specified search pattern. RegEx Module To use RegEx module, python comes with built-in package called re, which we need to work with Regular expression.
re.match()checks for a match only at the beginning of the string
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As others have alluded,
re.match starts from the beginning of the string-to-match and only checks for what is necessary. Notice
match='A cat' at the end of the object's string representation denotes what was matched:
r'(\w+) (\w+)' of
"A cat jumpped over a hat".
If you were to add a
$ to the end of your pattern, indicating the string-to-match should end there, it will not result in a match. And if you were to take that same pattern and shorten it to only two words, it would match once again:
>>> re.match(r'(\w+) (\w+)', "A cat jumpped over a hat") <_sre.SRE_Match object; span=(0, 5), match='A cat'> >>> re.match(r'(\w+) (\w+)$', "A cat jumpped over a hat") >>> re.match(r'(\w+) (\w+)$', "A cat") <_sre.SRE_Match object; span=(0, 5), match='A cat'>
Regular Expressions - Python Questions and Answers, 3 How to use Regular Expression in Python? 3.1 Import Re Module; 3.2 Use Raw String Argument; 3.3 RegEx Function Return Value. 4 Regular Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Learn more Questions About Regular Expressions in Python
Python Regular Expression a.k.a. RegEx for Beginners, Python RegEx are patterns that permit you to match various string the trending Python interview questions prepared by the industry experts. The match function matches the Python RegEx pattern to the string with optional flags. Syntax: re.match(pattern, string, flags=0) Where ‘pattern’ is a regular expression to be matched, and the second parameter is a Python String that will be searched to match the pattern at the starting of the string.
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