Strings in Python

Defining Strings in Python

Strings are defined using single (' ') or double (" ") quotes and are of type str. For multi-line text, triple quotes (''' ''' or """ """) can be used.

Strings are immutable, meaning their contents cannot be changed after creation.

my_str = "Python"
print(type(my_str))  # Output: <class 'str'>

Core Features of Strings

• Indexing: Access individual characters by position.
• Slicing: Extract specific portions using start:end syntax.
• Length: Use len() to count characters.
• Repetition: Use * to repeat strings.
• Concatenation: Use + to join strings.

Examples:

text = "Python"
print(text[0])           # Output: 'P'
print(text[1:4])         # Output: 'yth'
print(len(text))         # Output: 6
print(text * 2)          # Output: 'PythonPython'
print(text + " Rocks!")  # Output: 'Python Rocks!'

Common String Methods

Method	Description
str.lower()	Converts all characters to lowercase
str.upper()	Converts all characters to uppercase
str.strip()	Removes whitespace or specified characters from both ends
str.replace(old, new)	Replaces occurrences of a substring
str.find(sub)	Finds index of first occurrence of a substring
str.split(delimiter)	Splits string into list based on delimiter
str.join(list)	Joins list elements into a string using a separator
str.startswith(prefix)	Checks if string starts with specified prefix
str.endswith(suffix)	Checks if string ends with specified suffix
str.isdigit()	Returns True if string contains only digits

Usage Examples:

text = "  Python is Fun!  "

print(text.strip())                      # Removes leading/trailing spaces
print(text.lower())                      # Converts to lowercase
print(text.find("is"))                   # Output: 9
print(text.replace("Fun", "Powerful"))   # Replaces substring
print(text.split())                      # Output: ['Python', 'is', 'Fun!']
print("-".join(["A", "B", "C"]))         # Output: 'A-B-C'
print(text.startswith("Py"))            # False due to leading spaces
print("123".isdigit())                   # Output: True

Conclusion

Strings in Python are versatile and essential for text-based operations. From slicing and joining to formatting and condition checks, mastering string manipulation helps you write clean, expressive, and efficient Python code.