Format specifiers

Add a : inside the braces to control how a value looks:

f"{3.14159:.2f}"    # 3.14       2 decimal places
f"{1234567:,}"      # 1,234,567  thousands separator
f"{0.256:.1%}"      # 25.6%      percentage
f"{'hi':>6}"        # '    hi'   right-align in width 6

They combine: :,.2f means commas and 2 decimals.

See it run

pi = 3.14159
print(f"{pi:.2f}")
print(f"{pi:8.2f}|")
print(f"{pi}")

The bit after the colon inside {} is a format spec. It changes how a value is shown, never the value itself.

Practice format specifiers

Exercise 1

Print exactly two lines using format specifiers:

Price: $1,234.50 from price = 1234.5
Score: 87.5% from ratio = 0.875

Exercise 2

A weather widget shows one tidy line. Using city, temp and humidity, print exactly:

Oslo: -3.5°C, humidity 82%

the temperature with 1 decimal place
the humidity as a percentage with no decimals (.0%)

Exercise 3

Use the two items and prices in the code editor below to print a neat three-line receipt. Work out total = price1 + price2 first. On each line:

the label is left-aligned in width 10 (:<10)
the amount is right-aligned in width 7 with 2 decimals (:>7.2f)

The output should look like this:

Tea          3.50
Croissant    4.25
Total        7.75

Free lesson: use the editor to practice it.

Practice

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