7.25. Regex Flavors
In other programming languages
PCRE - Perl Compatible Regular Expressions
7.25.1. SetUp
import re
7.25.2. Enclosing
In Python we use raw-string (
r'...')In JavaScript we use
/pattern/flagsornew RegExp(pattern, flags)
Python:
r'[a-z]+'
JavaScript:
/[a-z]+/
JavaScript:
new RegExp("[a-z]")
7.25.3. Flags
In Python we use raw-string (
r'...')In JavaScript we use
/pattern/flagsornew RegExp(pattern, flags)
Python:
re.findall(r'[a-z]+', TEXT, flags=re.I)
re.findall(r'[a-z]+', TEXT, flags=re.IGNORECASE)
re.findall(r'[a-z]+', TEXT, flags=re.I|re.M)
re.findall(r'[a-z]+', TEXT, flags=re.IGNORECASE|re.MULTILINE)
JavaScript:
/[a-z]+/i
/[a-z]+/im
JavaScript:
new RegExp("[a-z]", "i") new RegExp("[a-z]", "im")
7.25.4. Named Groups
In Python we use
(?P<name>...)In JavaScript we use
(?<name>...)
Python:
r'(?P<mygroup>[a-z]+)'
JavaScript:
/(?<mygroup>[a-z]+)/
7.25.5. Range
[a-Z]==[a-zA-Z][a-9]==[a-zA-Z0-9]Works in other languages, but not in Python
Python:
r'[a-z]' # ok
r'[A-Z]' # ok
r'[A-z]' # ok
r'[a-Z]' # re.PatternError: bad character range a-Z at position 1
JavaScript:
/[a-Z]/ // SyntaxError: Invalid regular expression: /[a-Z]/: Range out of order in character class
Perl:
/[a-Z]/
7.25.6. Group Backreference
\g<name>- Python\g<1>- Python\1$1- grep, egrep, Jetbrains IDE
In JavaScript name groups don't have ?P but only ?:
Python:
r'(?P<name>\d+)'
JavaScript:
/(?<name>\d+)/
7.25.7. Named Ranges
[:alpha:]- Alphabetic character[a-zA-Z][:alnum:]- Alphabetic and numeric character[a-zA-Z0-9][:blank:]- Space or tab[:cntrl:]- Control character[:digit:]- Digit[:graph:]- Non-blank character (excludes spaces, control characters, and similar)[:lower:]- Lowercase alphabetical character[:print:]- Like [:graph:], but includes the space character[:punct:]- Punctuation character[:space:]- Whitespace character ([:blank:], newline, carriage return, etc.)[:upper:]- Uppercase alphabetical[:xdigit:]- Digit allowed in a hexadecimal number (i.e., 0-9a-fA-F)[:word:]- A character in one of the following Unicode general categories Letter, Mark, Number, Connector_Punctuation[:ascii:]- A character in the ASCII character set
In Python those Named Ranges does not work. String [:alpha:] will be
interpreted literally as either: : or a or l or p or h
or a.
TEXT = 'hello world'
re.findall(r'[:alpha:]', TEXT)
['h', 'l', 'l', 'l']