Control whether repetition consumes as much text as possible.
How It Works
Most Python regex quantifiers are greedy and attempt the longest match that permits success. Adding ? changes common quantifiers to non-greedy forms that prefer shorter spans, but neither mode makes parsing arbitrary HTML safe.
Step-by-Step Example
import re
source_text = '<b>One</b><b>Two</b>'
print(re.findall(r'<b>.*</b>', source_text))
print(re.findall(r'<b>.*?</b>', source_text))Understanding the Example
- The expression "'<b>One</b><b>Two</b>'" supplies the value stored as 'source_text'. This value is then used or checked by the later statements.
- The print() call exposes the result so you can compare it with the behavior described above. Check the value and its type when experimenting.
A successful run of this example prints the following output:
['<b>One</b><b>Two</b>']
['<b>One</b>', '<b>Two</b>']Where This Fits in a Real Program
Start by writing down examples that should match and examples that must fail. Check whether you need to locate a substring, match a prefix or validate an entire field; these are different operations. Unicode and escape sequences can also change which characters are matched, so test accented text and empty input.
Practice: Try It Yourself
Use an HTML parser rather than regex for nested or malformed HTML.
For this exercise, predict the result before running the changed code. Then explain the difference between the original and modified cases using the actual values, not just whether the program completed.
Further Reading
Read the official Python documentation for complete parameters, return types and exceptions.
Common Beginner Mistakes
- Using a greedy .* across several delimiters when each separate segment should be extracted.
- Compare greedy and non-greedy behavior on multiple quoted tokens.
Key Takeaways
- Control whether repetition consumes as much text as possible.
- Most Python regex quantifiers are greedy and attempt the longest match that permits success.
- Apply the demonstrated operation to the practice input and verify its result before depending on it in a larger program.