Python String Methods to Know for Intro to Python Programming

Understanding Python string methods is key to manipulating text effectively. These methods help with tasks like changing case, trimming spaces, splitting strings, and searching for substrings, making your coding experience smoother and more efficient.

1. str.lower()

   • Converts all characters in a string to lowercase.
   • Useful for case-insensitive comparisons.
   • Returns a new string; the original string remains unchanged.

2. str.upper()

   • Converts all characters in a string to uppercase.
   • Helpful for standardizing text input.
   • Returns a new string; the original string remains unchanged.

3. str.strip()

   • Removes leading and trailing whitespace from a string.
   • Can also remove specified characters by passing them as an argument.
   • Returns a new string; the original string remains unchanged.

4. str.split()

   • Divides a string into a list of substrings based on a specified delimiter (default is whitespace).
   • Useful for parsing data and processing user input.
   • Returns a list of strings.

5. str.join()

   • Combines elements of a list into a single string, using a specified separator.
   • Useful for creating formatted output from lists.
   • The separator is defined by the string on which the method is called.

6. str.replace()

   • Replaces occurrences of a specified substring with another substring.
   • Can limit the number of replacements by providing a count.
   • Returns a new string; the original string remains unchanged.

7. str.startswith()

   • Checks if a string starts with a specified substring.
   • Returns a boolean value (True or False).
   • Can check for multiple prefixes by passing a tuple.

8. str.endswith()

   • Checks if a string ends with a specified substring.
   • Returns a boolean value (True or False).
   • Can check for multiple suffixes by passing a tuple.

9. str.find()

   • Searches for a specified substring and returns the lowest index where it is found.
   • Returns -1 if the substring is not found.
   • Can specify a start and end index for the search.

10. str.count()

    • Counts the number of occurrences of a specified substring in a string.
    • Returns an integer representing the count.
    • Can specify a start and end index for the count.

11. str.isalpha()

    • Checks if all characters in a string are alphabetic.
    • Returns a boolean value (True or False).
    • Useful for validating user input.

12. str.isdigit()

    • Checks if all characters in a string are digits.
    • Returns a boolean value (True or False).
    • Useful for validating numeric input.

13. str.format()

    • Formats strings by inserting values into placeholders.
    • Supports various formatting options for numbers, dates, etc.
    • Returns a new formatted string.

14. str.len()

    • Returns the number of characters in a string.
    • Useful for determining string length for validation or processing.
    • Note: The correct function is

      len()

      not

      str.len()

      .

15. str.index()

    • Searches for a specified substring and returns the lowest index where it is found.
    • Raises a ValueError if the substring is not found.
    • Can specify a start and end index for the search.