Python Format String Specifiers: A Quick Reference Guide
Python provides multiple ways to format strings, with the most common methods being f-strings (f"") and
the .format() method.
1. Floating-Point Numbers
Limit to 2 decimal places
num = 12.34567
print(f"{num:.2f}") # 12.35
print("{:.2f}".format(num)) # 12.35
Fixed width with padding (10 chars, right-aligned)
print(f"{num:10.2f}") # ' 12.35'
Scientific notation
print(f"{num:.2e}") # 1.23e+01
2. Integers
Basic integer formatting
num = 42
print(f"{num:d}") # 42
Padding with spaces (width 5, right-aligned)
print(f"{num:5d}") # ' 42'
Padding with zeros (width 5, left-padded with zeros)
print(f"{num:05d}") # '00042'
Binary, Octal, Hex representations
print(f"{num:b}") # Binary: 101010
print(f"{num:o}") # Octal: 52
print(f"{num:x}") # Hex lowercase: 2a
print(f"{num:X}") # Hex uppercase: 2A
3. Strings
Fixed width with alignment
text = "Hi"
print(f"{text:10}") # 'Hi ' (right-aligned)
print(f"{text:<10}") # 'Hi ' (left-aligned)
print(f"{text:^10}") # ' Hi ' (center-aligned)
4. Percentages
Convert to percentage (multiplies by 100 and adds % sign)
fraction = 0.1234
print(f"{fraction:.2%}") # 12.34%
5. Thousand Separator
Use commas to format large numbers
big_num = 1234567890
print(f"{big_num:,}") # 1,234,567,890
For European-style separators (dot instead of comma)
print(f"{big_num:_}") # 1_234_567_890
Format Specifiers Cheat Sheet
| Specifier | Example | Description |
|---|---|---|
:.2f |
3.1415 → 3.14 |
2 decimal places |
:5d |
42 → ' 42' |
Right-align integer in 5 spaces |
:05d |
42 → '00042' |
Zero-padding for width 5 |
:.2e |
12345 → 1.23e+04 |
Scientific notation |
:b |
42 → '101010' |
Binary representation |
:o |
42 → '52' |
Octal representation |
:x |
42 → '2a' |
Hex lowercase |
:X |
42 → '2A' |
Hex uppercase |
:^10 |
"Hi" → ' Hi ' |
Center align |
:<10 |
"Hi" → 'Hi ' |
Left align |
:>10 |
"Hi" → ' Hi' |
Right align |
:, |
1234567 → '1,234,567' |
Thousands separator |
:.2% |
0.1234 → '12.34%' |
Convert to percentage |