Regular Expressions
Regex Flags
Python’s re module offers several flags that modify the behavior of regular expression operations. These flags are used as optional arguments to functions like re.compile(), re.search(), re.findall(), etc. They are combined using the bitwise OR operator (|).
Commonly Used Flags:
re.IGNORECASE(orre.I): Performs case-insensitive matching.'a'will match'A'.
import re
text = "Hello World"
match = re.search("world", text, re.IGNORECASE)
print(match) # <re.Match object; span=(6, 11), match='World'>
re.MULTILINE(orre.M): Makes^and$match the beginning and end of each line (instead of the entire string).
import re
text = """line one
line two
line three"""
matches = re.findall(r"^line", text, re.MULTILINE)
print(matches) # ['line', 'line', 'line']]
re.DOTALL(orre.S): Makes the.special character match any character, including newline characters (\n). Without this flag,.will not match newlines.
import re
text = "line one\nline two"
match = re.search(r".*", text, re.DOTALL)
print(match) # <re.Match object; span=(0, 16), match='line one\nline two'>
match = re.search(r".*", text) #Without DOTALL
print(match) # <re.Match object; span=(0, 9), match='line one'>
re.ASCII: Makes\w,\W,\b,\B,\d,\D,\s, and\Smatch only ASCII characters. Without this flag, they can also match Unicode characters.
import re
text = "Hello 世界"
match = re.findall(r"\w+", text) #Without ASCII flag
print(match) # ['Hello', '世界']]
match = re.findall(r"\w+", text, re.ASCII) #With ASCII flag
print(match) # ['Hello']]
re.VERBOSE(orre.X): Allows you to write more readable Regular Expressions by ignoring whitespace and adding comments.
import re
pattern = re.compile(r"""
\d+ # one or more digits
\s+ # one or more whitespace characters
[a-zA-Z]]+ # one or more letters
""", re.VERBOSE)
text = "123 abc"
match = pattern.search(text)
print(match) #<re.Match object; span=(0, 8), match='123 abc'>