Python f-strings: The Modern Way to Format Strings

F-strings (formatted string literals) have transformed string formatting in Python since their introduction in Python 3.6. Let’s explore some useful ways to use f-strings.

1. Number Formatting

Decimal Places

When working with floating-point numbers, controlling decimal places is crucial for readability:

ratio = 0.8544
print(f'{ratio:.2f}')  # Output: 0.85

Large Numbers

Make big numbers readable with automatic comma separation:

num = 100000000
print(f"{num:,}")  # Output: 100,000,000

2. Percentage Formatting

Converting decimals to percentages is a common task in data analysis and reporting:

ratio = 0.8544
print(f"{ratio:.1%}")  # Output: 85.4%

3. Date and Time Formatting

F-strings make date formatting intuitive and readable:

from datetime import datetime
date = datetime(2022, 1, 1, 15, 30, 45)
print(f"{date:%I:%M %p} on {date:%A}")  # Output: 03:30 PM on Saturday

4. Debug Printing

One of the most useful features for debugging is the ability to display variable names alongside their values:

for i in range(3):
    print(f"{i=}")
# Output:
# i=0
# i=1
# i=2