Python f-strings

Basic f-string Syntax

Add an f right before the opening quote, then place any variable or expression inside curly braces. Python evaluates the expression and inserts the result directly into the string at that position.

name = "Priya"
score = 87

print(f"Hello {name}, you scored {score} marks")
print(f"Next year you'll be {score + 1} points wiser")

Number Formatting

You can control how numbers appear by adding a colon and a format spec after the expression, for example limiting decimal places, adding thousands separators, or showing percentages.

price = 1234.5678
rate = 0.856

print(f"{price:.2f}")
print(f"{price:,.2f}")
print(f"{rate:.1%}")

1234.57
1,234.57
85.6%

Alignment and Width

You can pad and align text inside a fixed width using < for left, > for right, and ^ for center alignment, useful when printing neat tables in the terminal.

for item in ["Pen", "Notebook", "Bag"]:
    print(f"{item:<10}| in stock")

The Debug Specifier (=)

Since Python 3.8, adding = right after an expression prints both the expression text and its value, which is extremely handy for quick debugging without writing print("x =", x).

x = 42
y = x * 2
print(f"{x=} {y=}")

x=42 y=84

f-strings vs .format()

Before f-strings, Python developers used the .format() method, which works but is more verbose. f-strings are now the preferred style because they are shorter and easier to read.