f-strings in Python( starting from easy → medium → hard)

 

🟢 LEVEL 1: EASY — What is an f-string?

An f-string (formatted string literal) allows you to insert variables directly inside a string using {}.

✅ Basic syntax

name = "Raghav"
print(f"My name is {name}")

Output:

My name is Raghav

🟢 Why use f-strings?

• Easier than + concatenation

• Faster than format()

• Looks cleaner

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🟡 LEVEL 2: MEDIUM — Using Expressions in f-strings

You can insert calculations or functions inside { }.

Example:

a = 10
b = 5
print(f"Sum = {a+b}")

print(f"Uppercase: {'hello'.upper()}")

import math
print(f"Square root of 25 is {math.sqrt(25)}")

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🟡 Formatting numbers

✔ Decimal formatting

price = 49.5678
print(f"Price: {price:.2f}")   # 2 decimal places

✔ Add commas

num = 1000000
print(f"{num:,}")

✔ Percentage

rate = 0.75
print(f"{rate:.0%}")

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🔵 LEVEL 3: HARD — Formatting Alignment & Padding

⭐ Left, Center, Right Alignment

print(f"|{'Apple':<10}|")   # left
print(f"|{'Apple':>10}|")   # right
print(f"|{'Apple':^10}|")   # center

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⭐ Padding with characters

print(f"{5:05}")   # 00005
print(f"{42:*^10}") # ****42****

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🔵 Using Dictionaries in f-strings

student = {"name": "Raghav", "age": 20}
print(f"Name: {student['name']}, Age: {student['age']}")

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🔵 Nested f-strings (tricky but powerful)

name = "Raghav"
style = "upper"

print(f"{name.{style}()}")   # ❌ This will not work

Correct way:

print(f"{getattr(name, style)()}")

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🟣 LEVEL 4: ADVANCED — Using f-strings for debugging

Python 3.8+ allows:

x = 10
y = 20
print(f"{x=}, {y=}")

Output:

x=10, y=20

This is extremely useful for debugging.

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🟣 Embedding conditional (if) in f-strings

age = 18
print(f"You are {'adult' if age >= 18 else 'minor'}")

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🟣 Format dates using f-strings

from datetime import datetime

now = datetime.now()
print(f"Today is {now:%d-%m-%Y}")

Output:

Today is 14-11-2025

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🔴 LEVEL 5: EXTREME — Using f-strings with classes

class Student:
    def __init__(self, name, marks):
        self.name = name
        self.marks = marks

s = Student("Raghav", 95)

print(f"Student: {s.name}, Marks: {s.marks}")

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🔴 Custom formatting using __format__

class Money:
    def __init__(self, amount):
        self.amount = amount

    def __format__(self, fmt):
        if fmt == "INR":
            return f"₹{self.amount:.2f}"
        return str(self.amount)

m = Money(500)
print(f"Total Amount: {m:INR}")

Output:

Total Amount: ₹500.00

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🏁 SUMMARY

Level	What You Learned
Easy	Basic f-string usage
Medium	Expressions, functions, number formatting
Hard	Alignment, padding, dictionary access
Advanced	Debugging, conditions, date formatting
Expert	Classes + custom formatting