Python String Methods Overview

Overview

This lecture covers three important Python string methods: isalpha(), isnumeric(), and isalnum(), explaining their purpose, syntax, and behavior with examples. A homework problem is also provided for practice.

isalpha() Method

• isalpha() returns True if all characters in a string are alphabetic (A-Z, a-z), with no spaces or other characters.
• Syntax: string.isalpha()
• Example: "hello2".isalpha() returns False because '2' is not an alphabet.
• Example: "helloIAmJustpreet".isalpha() returns True since all characters are letters.
• Example: "hello I am justpreet".isalpha() returns False due to spaces.

isnumeric() Method

• isnumeric() returns True if all characters in a string are numeric digits (0-9), no dots, minus signs, or other symbols allowed.
• Syntax: string.isnumeric()
• Example: "2332324".isnumeric() returns True.
• Example: "3.14159".isnumeric() returns False because the dot is not numeric.
• Example: "2/4".isnumeric() returns False as '/' is not a digit.
• Example: "-3425".isnumeric() returns False because '-' is not a digit.

isalnum() Method

• isalnum() returns True if all characters in a string are either alphabetic or numeric (no spaces or special characters).
• Syntax: string.isalnum()
• Example: "justpreet20".isalnum() returns True (letters and digits only).
• Example: "22324242".isalnum() returns True (digits only).
• Example: "JustBreathe".isalnum() returns True (letters only).
• Example: "Just preet".isalnum() returns False due to the space.

Key Terms & Definitions

• Alphabetic characters — Letters only (A-Z, a-z), no spaces or numbers.
• Numeric characters — Digits only (0-9), no signs, decimals, or spaces.
• Alphanumeric characters — Combination of letters and numbers, no spaces or special characters.

Action Items / Next Steps

• Solve the homework: Determine and write the output for each given line of code using the isalpha(), isnumeric(), and isalnum() methods before checking in Python.