Learn how to work with text in Python — string methods, formatting, and modern f-strings.

Strings

A string is a sequence of characters used to represent text. Anything inside quotes is a string — letters, numbers, symbols, spaces, all of it.

name = "Ali"
message = 'Hello, world!'
mixed = "I have 3 cats and 2 dogs."

You already saw strings in the basics section. This file goes deep — methods, formatting, searching, cleaning, and modern f-strings.

Creating strings

# single or double quotes — both work the same
name = "Ali"
city = 'Lahore'

# triple quotes — for multiline text
bio = """
My name is Ali.
I am from Lahore.
I love Python.
"""

# escape characters
path = "C:\\Users\\Ali\\Documents"
tab = "name\tage\tcity"
newline = "line one\nline two"

Common escape characters:

Escape	Meaning
`\n`	New line
`\t`	Tab
`\\`	Backslash
`\"`	Double quote
`\'`	Single quote

Raw strings — ignore escape characters completely:

path = r"C:\Users\Ali\Documents"
print(path)   # C:\Users\Ali\Documents — backslashes stay as-is

Accessing characters

Strings are sequences — you can access characters by index, just like lists:

name = "Python"
#       012345

print(name[0])    # P
print(name[-1])   # n — last character
print(name[1:4])  # yth — slicing
print(name[::-1]) # nohtyP — reversed

Strings are immutable — you cannot change a character directly:

name = "Python"
name[0] = "J"   # TypeError — strings cannot be modified in place

To "change" a string, you create a new one.

String methods

Python gives you a large set of built-in methods to work with strings. None of them modify the original — they always return a new string.

Case methods

text = "hello world"

print(text.upper())       # HELLO WORLD
print(text.lower())       # hello world
print(text.capitalize())  # Hello world — first letter uppercase only
print(text.title())       # Hello World — first letter of each word
print(text.swapcase())    # HELLO WORLD → hello world and vice versa

Real use — case-insensitive comparison:

user_input = "PYTHON"

if user_input.lower() == "python":
    print("Correct!")

Stripping whitespace

text = "   hello world   "

print(text.strip())    # "hello world" — removes from both sides
print(text.lstrip())   # "hello world   " — removes from left only
print(text.rstrip())   # "   hello world" — removes from right only

You can also strip specific characters:

text = "###hello###"
print(text.strip("#"))   # hello

Very commonly used when cleaning user input or reading files.

Finding and checking

text = "Python is great and Python is fun"

print(text.find("Python"))      # 0 — index of first match
print(text.find("Java"))        # -1 — not found, no error
print(text.rfind("Python"))     # 18 — index of last match
print(text.index("Python"))     # 0 — like find but raises ValueError if not found
print(text.count("Python"))     # 2 — how many times it appears

Checking content:

print("hello".startswith("he"))    # True
print("hello".endswith("lo"))      # True
print("hello".startswith("lo"))    # False

Checking what the string contains:

print("Ali123".isalnum())    # True  — only letters and numbers
print("Ali".isalpha())       # True  — only letters
print("123".isdigit())       # True  — only digits
print("   ".isspace())       # True  — only whitespace
print("Hello World".istitle()) # True — title case

Replacing

text = "I love Java. Java is great."

print(text.replace("Java", "Python"))
# I love Python. Python is great.

# replace only the first occurrence
print(text.replace("Java", "Python", 1))
# I love Python. Java is great.

Removing prefixes and suffixes (Python 3.9+)

filename = "report_2024.pdf"

print(filename.removesuffix(".pdf"))    # report_2024
print(filename.removeprefix("report_")) # 2024.pdf

Much cleaner than the old way of slicing strings manually.

url = "https://example.com"
print(url.removeprefix("https://"))   # example.com

Splitting and joining

split() — break a string into a list:

sentence = "Python is easy to learn"

words = sentence.split()       # splits on whitespace by default
print(words)   # ['Python', 'is', 'easy', 'to', 'learn']

csv = "ali,sara,omar,fatima"
names = csv.split(",")
print(names)   # ['ali', 'sara', 'omar', 'fatima']

Split with a limit:

text = "one:two:three:four"
print(text.split(":", 2))   # ['one', 'two', 'three:four']

join() — combine a list into a string:

words = ["Python", "is", "easy", "to", "learn"]

sentence = " ".join(words)
print(sentence)   # Python is easy to learn

csv = ",".join(["ali", "sara", "omar"])
print(csv)        # ali,sara,omar

path = "/".join(["home", "ali", "documents"])
print(path)       # home/ali/documents

join() is called on the separator, not the list. " ".join(words) — the space is the separator, words is the list. This trips up beginners at first but becomes natural quickly.

Padding and alignment

text = "Ali"

print(text.ljust(10))         # "Ali       " — left aligned, padded to 10
print(text.rjust(10))         # "       Ali" — right aligned
print(text.center(10))        # "   Ali    " — centered
print(text.center(10, "-"))   # "---Ali----" — centered with fill character
print("42".zfill(5))          # "00042" — pad with zeros on the left

in — check if substring exists

text = "Python is amazing"

print("Python" in text)      # True
print("Java" in text)        # False
print("python" in text)      # False — case sensitive
print("python" in text.lower())  # True

f-strings — modern string formatting

f-strings are the cleanest way to build strings with variables. Put f before the quote and wrap expressions in {}.

name = "Ali"
age = 22

print(f"My name is {name} and I am {age} years old.")
# My name is Ali and I am 22 years old.

You can put any expression inside {}:

a = 10
b = 3

print(f"{a} + {b} = {a + b}")
print(f"{a} / {b} = {a / b:.2f}")
print(f"{'hello'.upper()}")
print(f"{2 ** 10}")

Number formatting in f-strings

price = 1234567.891

print(f"{price:.2f}")        # 1234567.89 — 2 decimal places
print(f"{price:,.2f}")       # 1,234,567.89 — thousands separator
print(f"{price:e}")          # 1.234568e+06 — scientific notation
print(f"{0.1 + 0.2:.1f}")   # 0.3 — clean up float imprecision

score = 0.873
print(f"{score:.1%}")        # 87.3% — as percentage

number = 255
print(f"{number:b}")         # 11111111 — binary
print(f"{number:x}")         # ff — hexadecimal
print(f"{number:o}")         # 377 — octal

Alignment in f-strings

items = [("Apple", 1.50), ("Banana", 0.75), ("Mango", 2.00)]

print(f"{'Item':<10} {'Price':>8}")
print("-" * 20)
for name, price in items:
    print(f"{name:<10} {price:>8.2f}")

Output:

Item          Price
--------------------
Apple          1.50
Banana         0.75
Mango          2.00

< means left-align, > means right-align, the number is the width.

Python 3.12 f-string improvements

Python 3.12 made f-strings much more flexible. You can now use the same quote type inside {} — no more escaping:

# Before Python 3.12 — had to use different quotes inside
student = {"name": "Ali"}
print(f"Name: {student['name']}")   # had to use single quotes inside

# Python 3.12+ — same quotes work fine
print(f"Name: {student["name"]}")   # works perfectly now

You can also use backslashes inside f-string expressions in Python 3.12+:

names = ["Ali", "Sara", "Omar"]

# Python 3.12+
print(f"Names: {'\n'.join(names)}")

And multi-line f-strings with complex expressions are now properly supported:

scores = [88, 92, 79, 95]

result = f"""
Students: {len(scores)}
Average:  {sum(scores) / len(scores):.1f}
Highest:  {max(scores)}
Lowest:   {min(scores)}
"""
print(result)

= specifier — debugging shortcut

Very useful when debugging — prints the variable name and its value:

name = "Ali"
age = 22
score = 88.5

print(f"{name=}")     # name='Ali'
print(f"{age=}")      # age=22
print(f"{score=}")    # score=88.5
print(f"{2 + 2=}")    # 2 + 2=4

String repetition and concatenation

# concatenation
greeting = "Hello" + ", " + "world!"
print(greeting)   # Hello, world!

# repetition
line = "-" * 30
print(line)   # ------------------------------

border = "=" * 20
title = "REPORT"
print(border)
print(title.center(20))
print(border)

Multiline strings

message = """
Dear Ali,

Your order has been confirmed.
Total: $49.99

Thank you for shopping with us.
"""

print(message)

A real example

A simple receipt generator:

def generate_receipt(customer, items):
    width = 35
    print("=" * width)
    print(f"{'RECEIPT':^{width}}")
    print("=" * width)
    print(f"Customer: {customer}")
    print("-" * width)
    print(f"{'Item':<20} {'Price':>10}")
    print("-" * width)

    total = 0
    for item, price in items:
        print(f"{item:<20} {price:>10.2f}")
        total += price

    print("-" * width)
    print(f"{'TOTAL':<20} {total:>10.2f}")
    print("=" * width)

items = [
    ("Python Book", 29.99),
    ("USB Cable", 9.99),
    ("Mouse Pad", 7.50),
]

generate_receipt("Ali Ahmed", items)

Output:

===================================
              RECEIPT              
===================================
Customer: Ali Ahmed
-----------------------------------
Item                      Price
-----------------------------------
Python Book               29.99
USB Cable                  9.99
Mouse Pad                  7.50
-----------------------------------
TOTAL                     47.48
===================================

Summary

Method	What it does
`upper()` / `lower()`	Change case
`strip()` / `lstrip()` / `rstrip()`	Remove whitespace
`find(x)` / `rfind(x)`	Find index of substring
`count(x)`	Count occurrences
`replace(old, new)`	Replace substring
`removeprefix(x)`	Remove prefix (3.9+)
`removesuffix(x)`	Remove suffix (3.9+)
`split(sep)`	Split into list
`join(list)`	Join list into string
`startswith(x)` / `endswith(x)`	Check start or end
`isdigit()` / `isalpha()` / `isalnum()`	Check content type
`center()` / `ljust()` / `rjust()`	Align text
`zfill(n)`	Pad with zeros
`f"{var=}"`	Debug print with name

Strings

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