Verify that a pattern matches a complete input value.
How It Works
re.fullmatch(pattern, string) requires the entire text to fit the pattern, returning a Match object or None. It is well suited to format checks, but it does not guarantee an email address, telephone number, or URL is genuinely reachable.
Step-by-Step Example
import re
code_pattern = r'[A-Z]{2}-\d{4}'
print(bool(re.fullmatch(code_pattern, 'AB-2026')))
print(bool(re.fullmatch(code_pattern, 'AB-2026 extra')))Understanding the Example
- The expression "r'[A-Z]{2}-\\d{4}'" supplies the value stored as 'code_pattern'. 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:
True
FalseWhere 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
Check format separately from business rules and database uniqueness.
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 search() for validation and accepting extra characters outside the intended pattern.
- Validate an identifier consisting of three uppercase letters and five digits.
Key Takeaways
- Verify that a pattern matches a complete input value.
- re.fullmatch(pattern, string) requires the entire text to fit the pattern, returning a Match object or None.
- Apply the demonstrated operation to the practice input and verify its result before depending on it in a larger program.