String methods in Python

Strings in Python are sequences of characters. In Python, strings have a variety of built-in methods that allow you to manipulate and work with text data.

Here are some commonly used string methods:

1. upper() method The upper method converts all characters in the string to uppercase.

Syntax string.upper()

Example:

Python

text = "hello world"

# Convert to uppercase
print(text.upper())   # Output: HELLO WORLD

Special Note: • Does not modify the original string (strings are immutable in Python).
• Returns a new string.

2. lower() method The lower() method converts all characters of a string to lowercase.

Syntax string.lower()

Example:

Python

text = "HELLO WORLD"
print(text.lower())   # Output: hello world

Special Note: • Returns a new string.
• Useful for case-insensitive comparisons.

3. title() method The title method converts the first character of each word to uppercase and the rest to lowercase.

Syntax string.title()

Example:

Python

text = "welcome to python programming"
print(text.title())
# Output: Welcome To Python Programming

4. capitalize() method The capitalize method capitalizes the first character of the string and makes all other characters lowercase.

Syntax string.capitalize()

Example:

Python

text = "ashish is a good boy. he Loves Swimming."
print(text.capitalize())   
# Output: Ashish is a good boy. he loves swimming.

Special Note: As string in Python is immutable, so any operation on it returns a new string.

5. replace() method The replace() method replaces all occurrences of a substring with another.

Syntax string.replace(old, new, count)

Example:

Python

text = "I like Java. Java is popular."
print(text.replace("Java", "Python"))   
# Output: I like Python. Python is popular.

Special Note: • The count parameter limits replacements.
• Returns a new string.

6. split() Method The split method splits the string into a list using a delimiter.

Syntax string.split(separator, maxsplit)

• Separator: We can specify the separator; default separator is any whitespace.

Example: Split a string into a list where each word is a list item.

Python

text = "apple,banana,cherry"
print(text.split(","))   
# Output: ['apple', 'banana', 'cherry']

7. count() method The count method returns the number of occurrences of a substring.

Syntax string.count(substring, start, end)

Example:

Python

text = "banana"
print(text.count("a"))   # Output: 3

8. find() method The find() method returns the lowest index of substring (first occurrence).

Syntax string.find(substring, start, end)

Example:

Python

text = "python programming"
print(text.find("pro"))   # Output: 7

Special Note: Returns -1 if substring is not found.

9. rfind() method The rfind() method returns the highest index (last occurrence).

Syntax string.rfind(substring, start, end)

Example:

Python

text = "python programming"
print(text.rfind("m"))    # Output: 14

Special Note: Returns -1 if substring is not found.

10. swapcase() method The swapcase() method converts uppercase letters to lowercase and lowercase letters to uppercase.

Syntax string.swapcase()

Example:

Python

text = "PyThOn"
print(text.swapcase())   # Output: pYtHoN

11. startswith() method The startswith() method checks if a string begins with the specified prefix.
• The prefix can be a string or a tuple of strings.
• Optional arguments start and end let you restrict the search to a slice of the string.

Syntax string.startswith(prefix, start, end)

Example: Basic usage.

Python

filename = "python_programming.txt"
print(filename.startswith("python"))   # True

Example: Using a tuple of prefixes.

Python

languages = ["python", "java", "csharp", "cpp"]
for lang in languages:
    if lang.startswith(("py", "ja")):   # tuple of prefixes
        print(lang)   # prints 'python' and 'java'

Example: With start and end parameters.

Python

text = "python programming"
print(text.startswith("program", 7, 18))   # True

12. endswith() method The endswith() method checks if a string ends with the specified suffix.
• The suffix can be a string or a tuple of strings.
• Optional arguments start and end let you restrict the search to a substring.

Syntax string.endswith(suffix, start, end)

Example: Basic usage.

Python

filename = "python_programming.txt"
print(filename.endswith(".txt"))    # True

Example: Using a tuple of suffixes.

Python

files = ["report.pdf", "data.csv", "script.py", "notes.txt"]
for f in files:
    if f.endswith((".csv", ".txt")):   # tuple of suffixes
        print(f)   # prints 'data.csv' and 'notes.txt'

Example: With start and end parameters.

Python

text = "learn_python_basics"
print(text.endswith("python", 6, 12))   # True

13. format() method The format method formats a string using placeholders {}.

Syntax string.format(values...)

Example:

Python

name = "Ashish"
age = 29
print("My name is {} and I am {} years old.".format(name, age))
# Output: My name is Ashish and I am 29 years old.

14. join() method The join() method joins elements of an iterable into a single string using the given separator.

Syntax separator.join(iterable)

Example:

Python

fruits = ["apple", "banana", "cherry"]
print(" - ".join(fruits))  
# Output: apple - banana - cherry

Special Note: Only works with iterables of strings.

15. len() method The len() function returns the number of characters in a string.
• It counts letters, digits, spaces, special symbols, and emojis.
• It does not skip spaces or hidden characters like \n (newline) or \t (tab).

Syntax len(string)

• string → Any valid string (sequence of characters).

Example:

Python

text = "Hello"
print(len(text))   # Output: 5

Example: String with Spaces.

Python

text = "Hello World"
print(len(text))   # Output: 11
# Includes the space between Hello and World