Python Strings : String Methods

Python provides a rich set of string methods to manipulate, modify, and analyze strings. These methods help you perform common tasks like searching, formatting, changing case, and more. Below is a list of commonly used string methods in Python with examples.

1. upper()

Converts all characters in the string to uppercase.

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

2. lower()

Converts all characters in the string to lowercase.

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

3. capitalize()

Capitalizes the first character of the string and converts the rest to lowercase.

text = "hello world"
result = text.capitalize()
print(result)  # Output: "Hello world"

4. title()

Converts the first character of each word to uppercase.

text = "hello world"
result = text.title()
print(result)  # Output: "Hello World"

5. strip()

Removes leading and trailing whitespace characters (or other specified characters).

text = "   hello world   "
result = text.strip()
print(result)  # Output: "hello world"

You can also remove specific characters by passing them as an argument:

text = "###hello world###"
result = text.strip('#')
print(result)  # Output: "hello world"

6. lstrip() and rstrip()

Removes leading (left) or trailing (right) whitespace or specified characters.

text = "   hello world   "
print(text.lstrip())  # Output: "hello world   "
print(text.rstrip())  # Output: "   hello world"

7. split()

Splits the string into a list of substrings based on a delimiter (default is whitespace).

text = "hello world python"
result = text.split()
print(result)  # Output: ['hello', 'world', 'python']

# Split by a specific delimiter
text = "apple,banana,cherry"
result = text.split(',')
print(result)  # Output: ['apple', 'banana', 'cherry']

8. join()

Joins a list of strings into a single string, with a specified separator.

words = ['hello', 'world', 'python']
result = " ".join(words)
print(result)  # Output: "hello world python"

9. replace()

Replaces occurrences of a substring with another substring.

text = "hello world"
result = text.replace("world", "python")
print(result)  # Output: "hello python"

10. find()

Returns the index of the first occurrence of a substring. Returns -1 if the substring is not found.

text = "hello world"
index = text.find("world")
print(index)  # Output: 6

index = text.find("python")
print(index)  # Output: -1

11. index()

Similar to find(), but raises a ValueError if the substring is not found.

text = "hello world"
index = text.index("world")
print(index)  # Output: 6

# Raises ValueError if the substring is not found
# text.index("python")  # ValueError: substring not found

12. startswith() and endswith()

Checks if the string starts or ends with a particular substring.

text = "hello world"
print(text.startswith("hello"))  # Output: True
print(text.endswith("world"))    # Output: True

13. count()

Returns the number of occurrences of a substring in the string.

text = "hello hello world"
count = text.count("hello")
print(count)  # Output: 2

14. isalpha()

Checks if all characters in the string are alphabetic.

text = "hello"
print(text.isalpha())  # Output: True

text = "hello123"
print(text.isalpha())  # Output: False

15. isdigit()

Checks if all characters in the string are digits.

text = "12345"
print(text.isdigit())  # Output: True

text = "12345abc"
print(text.isdigit())  # Output: False

16. isalnum()

Checks if all characters in the string are alphanumeric (letters and numbers).

text = "hello123"
print(text.isalnum())  # Output: True

text = "hello 123"
print(text.isalnum())  # Output: False (space is not alphanumeric)

17. isspace()

Checks if the string consists only of whitespace characters.

text = "   "
print(text.isspace())  # Output: True

text = "hello world"
print(text.isspace())  # Output: False

18. swapcase()

Converts uppercase characters to lowercase and lowercase characters to uppercase.

text = "Hello World"
result = text.swapcase()
print(result)  # Output: "hELLO wORLD"

19. zfill()

Pads the string on the left with zeros until it reaches a specified length.

text = "42"
result = text.zfill(5)
print(result)  # Output: "00042"

20. center(), ljust(), and rjust()

• center(): Centers the string in a field of a specified width.
• ljust(): Left-justifies the string.
• rjust(): Right-justifies the string.

text = "hello"
print(text.center(10, '-'))  # Output: "--hello---"
print(text.ljust(10, '-'))   # Output: "hello-----"
print(text.rjust(10, '-'))   # Output: "-----hello"

21. format()

Inserts values into placeholders within the string.

name = "John"
age = 30
result = "My name is {} and I am {} years old.".format(name, age)
print(result)  # Output: "My name is John and I am 30 years old."

22. partition() and rpartition()

Splits the string at the first (or last) occurrence of a specified separator, returning a tuple of three parts: the part before the separator, the separator itself, and the part after the separator.

text = "hello world"
result = text.partition(" ")
print(result)  # Output: ('hello', ' ', 'world')

result = text.rpartition(" ")
print(result)  # Output: ('hello', ' ', 'world')

These are just a few of the powerful string methods Python provides.