Track 7 · Lesson 5 of 11

Validating text

Check that input has the right shape using isdigit, isalpha and friends (and their Unicode caveats), then combine small checks into validators.

You will be able to

• Use isdigit(), isdecimal(), isalpha(), isalnum(), isspace(), isupper() and islower() and predict their results on edge cases
• Explain why isdigit() accepts characters such as ² and Arabic-Indic digits, and restrict a check to ASCII when needed
• Write validator functions that combine length, position and character checks with early returns
• Validate realistic formats: PIN codes, product codes, email addresses and phone numbers