How to match pattern over multiple lines in Python?

Learning Python's Regular Expressions (Regex) may require you to match text that spans multiple lines. This commonly occurs when reading information from files or scraping data from websites.

This article demonstrates how to match patterns across multiple lines using Python's re module with special flags like re.DOTALL and re.MULTILINE.

Understanding Multi-line Pattern Matching

By default, the dot metacharacter . in regular expressions matches any character except newline characters. To match patterns that span multiple lines, Python's re module provides special flags that modify this behavior ?

• re.DOTALL: Makes . match any character including newlines

• re.MULTILINE: Makes ^ and $ match start/end of each line, not just the entire string

Using re.DOTALL Flag

The re.DOTALL flag allows the dot . to match newline characters, enabling pattern matching across multiple lines ?

import re

paragraph = '''
<p>
Tutorials point is a website.
It is a platform to enhance your skills.
</p>
'''

match = re.search(r'<p>.*</p>', paragraph, re.DOTALL)
if match:
    print(match.group(0))

<p>
Tutorials point is a website.
It is a platform to enhance your skills.
</p>

Using re.MULTILINE Flag

The re.MULTILINE flag makes ^ and $ match the start and end of each line, not just the entire string ?

import re

text = """Hello world.
It is a beautiful day.
It will work!"""

matches = re.findall(r"^It.*", text, re.MULTILINE)
print("Matches found:", matches)

Matches found: ['It is a beautiful day.', 'It will work!']

Complex Multi-line Patterns

You can combine flags and create complex patterns. Here's how to find lines starting with "It" and ending with a period ?

import re

multi_line_text = """Hello world.
It is a beautiful day.
This is a test.
It will work!"""

pattern = r'(^It.*\.)'
matches = re.findall(pattern, multi_line_text, re.MULTILINE)
print("Matches found:", matches)

Matches found: ['It is a beautiful day.']

Matching HTML Blocks

Use re.DOTALL to match HTML blocks that span multiple lines ?

import re

html = """<div>
<p>Hello</p>
<p>Welcome</p>
</div>"""

pattern = r"<div>.*</div>"
match = re.search(pattern, html, re.DOTALL)
if match:
    print(match.group())

<div>
<p>Hello</p>
<p>Welcome</p>
</div>

Comparison of Flags

Conclusion

Use re.DOTALL when you need to match patterns spanning multiple lines. Use re.MULTILINE when you want to match patterns at the beginning or end of individual lines within multi-line text.