Python Regular Expression
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1. References
http://docs.python.org/library/re.html#module-re
http://docs.python.org/library/re.html#raw-string-notation
http://docs.python.org/howto/regex.html#regex-howto
"mastering regular expression"
2. an example in bitbake
'(?P_append|_prepend)(_(?P.*))?'
This regular expression matches strings which have form 'xxx_append' or 'xxx_prepend' or 'xxx_append_yyy' or 'xxx_prepend_yyy'.
Let's take a simple analysis on it.
REGEXP = '(?P_append|_prepend)(_(?P.*))?' = ABC? (match AB or ABC)
A = '(?P
B = '(?P_append|_prepend) matches '_append' or '_prepend'.
C = (_(?P.*)) matches string like '_xxxxxxxxx'
Following the test code for this regular expression the the corresponding output in shell.
chenqi@chenqi-OptiPlex-760:~/mypro/python$ ./test_regexp.py ('(?P_append|_prepend)(_(?P.*))?', 'hello_append', '_append', None, 'hello_append') ('(?P_append|_prepend)(_(?P.*))?', 'hello', None) ('(?P_append|_prepend)(_(?P.*))?', 'hello_prepend', '_prepend', None, 'hello_prepend') ('(?P_append|_prepend)(_(?P.*))?', 'hello_append_add_package', '_append', 'add_package', 'hello_append_add_package') ('(?P_append|_prepend)(_(?P.*))?', 'hello_append_world_package', '_append', 'world_package', 'hello_append_world_package')
3. a complete list of metacharacters
4. predefined special sequences
\d
Matches any decimal digit; this is equivalent to the class
[0-9].
\D
Matches any non-digit character; this is equivalent to the class
[^0-9].
\s
Matches any whitespace character; this is equivalent to the class
[
\t\r\f\v].
\S
Matches any non-whitespace character; this is equivalent to the class
[^
\t\r\f\v].
\w
Matches any alphanumeric character; this is equivalent to the class
[a-zA-Z0-9_].
\W
Matches any non-alphanumeric character; this is equivalent to the class[^a-zA-Z0-9_].
To Be Continue ...
http://docs.python.org/library/re.html#module-re
http://docs.python.org/library/re.html#raw-string-notation
http://docs.python.org/howto/regex.html#regex-howto
"mastering regular expression"
2. an example in bitbake
'(?P
This regular expression matches strings which have form 'xxx_append' or 'xxx_prepend' or 'xxx_append_yyy' or 'xxx_prepend_yyy'.
Let's take a simple analysis on it.
REGEXP = '(?P
A = '(?P
B = '(?P
C = (_(?P
Following the test code for this regular expression the the corresponding output in shell.
#!/usr/bin/env python
# test_regexp.py regexp string
import sys
import re
#pattern = sys.argv[1]
#string = sys.argv[2]
def test(pattern, string):
result = re.match(pattern, string)
if result == None:
print (pattern, string, None)
else:
print (pattern, string, result.group('keyword'), result.group('add'), result.group(0))
pattern = '(?P<base>.*?)(?P<keyword>_append|_prepend)(_(?P<add>.*))?'
test(pattern, 'hello_append')
test(pattern, 'hello')
test(pattern, 'hello_prepend')
test(pattern, 'hello_append_add_package')
test(pattern, 'hello_append_world_package')chenqi@chenqi-OptiPlex-760:~/mypro/python$ ./test_regexp.py ('(?P
3. a complete list of metacharacters
. ^ $ * + ? { } [ ] \ | ( )4. predefined special sequences
\d
Matches any decimal digit; this is equivalent to the class
[0-9].
\D
Matches any non-digit character; this is equivalent to the class
[^0-9].
\s
Matches any whitespace character; this is equivalent to the class
[
\t\r\f\v].
\S
Matches any non-whitespace character; this is equivalent to the class
[^
\t\r\f\v].
\w
Matches any alphanumeric character; this is equivalent to the class
[a-zA-Z0-9_].
\W
Matches any non-alphanumeric character; this is equivalent to the class[^a-zA-Z0-9_].
To Be Continue ...