Strings in Python are ordered sequences of Unicode characters enclosed in single quotes '...', double quotes "...", or triple quotes """...""".
Crucial Rule: Strings are immutable. Once created, you cannot change individual characters in-place (e.g. s[0] = 'X' raises TypeError). You must create a new string object instead.
s[0:3] -> Characters from index 0 up to (but not including) index 3.s[2:] -> From index 2 to the end of string.s[:4] -> From start up to index 4.s[::-1] -> Step is -1: reverses the entire string!Introduced in Python 3.6, f-strings provide the cleanest way to interpolate variables and expressions directly inside strings:
name = "Balaji"
score = 98.456
print(f"Student: {name}, Score: {score:.2f}%")text = "Python Programming in 2026"
# Indexing and Slicing
print("Original Text:", text)
print("First Char [0]:", text[0])
print("Last Char [-1]:", text[-1])
print("Slice [0:6]:", text[0:6])
print("Reversed [::-1]:", text[::-1])
# Essential String Methods
sample = " hello, world! python is awesome. "
print("
Cleaned & Formatted:")
print("strip():", sample.strip())
print("upper():", sample.strip().upper())
print("title():", sample.strip().title())
print("replace():", sample.strip().replace("world", "developers"))
# Splitting and Joining
words = text.split(" ")
print("
Split into words list:", words)
print("Joined with hyphens:", "-".join(words))Writing s[0] = "H" raises TypeError: "str" object does not support item assignment. Instead, use slicing: s = "H" + s[1:]
Check whether a word or phrase reads identically backwards and forwards.
def check_palindrome(word: str) -> bool:
cleaned = word.lower().replace(" ", "")
return cleaned == cleaned[::-1]
test_words = ["racecar", "Python", "madam", "Never odd or even"]
for w in test_words:
result = "✅ Palindrome" if check_palindrome(w) else "❌ Not palindrome"
print(f"'{w}' -> {result}")F-strings are evaluated at runtime directly as optimized bytecode expressions rather than parsing format specification strings.