Python String Format

String formatting means inserting values into a string and controlling how those values appear. In modern Python, f-strings are usually the simplest option.

Tested on: Python 3.13.3; kernel 6.14.0-37-generic.

Quick answer: format a string in Python

Use f"{name}" for modern formatting. Use "{}".format(value) for str.format(). Use "%s" % value mainly for older code.

name = "Deepak"
price = 19.99

print(f"Hello {name}")
print("Hello {}".format(name))
print("Price: %.2f" % price)

Each line builds a formatted string with a different style. For appending text without full formatting rules, see Append string in Python.

Python string format quick reference

What is string formatting in Python?

String formatting inserts values into a string. It can also control width, alignment, padding, decimal places, signs, commas, percentages, and dates. For joining plain text without format specifiers, see Python concatenate strings.

Python has three common styles:

• f-strings — best for most modern code
• str.format() — useful for reusable templates
• Percent formatting — common in older code

Best way to format strings in modern Python

Use f-strings for most new Python 3.6+ code. They are readable and allow variables and expressions inside braces.

Use str.format() when you need a reusable template string stored separately from the values. Use percent formatting mainly for older code or logging-style patterns you already see in existing projects. When you only need to test whether two formatted values match, compare strings after normalizing case or whitespace if needed.

Python f-string format

Syntax: f"text {value}"

Variables and expressions go inside curly braces. f-strings are evaluated at runtime.

name = "Deepak"
qty = 3
price = 4.50

print(f"Hello {name}")
print(f"Total: {qty * price:.2f}")

This should be your default choice in new Python code.

Format variables with f-strings

name = "Deepak"
roll = 4359
subject = "Python"

print(f"Hello {name}, your roll number is {roll}")
print(f"{name} is studying {subject}")

Insert strings, integers, and simple expressions directly in the sentence.

Format numbers with f-strings

num = 1234567
price = 19.995
ratio = 0.25

print(f"{num:d}")
print(f"{num:,}")
print(f"{price:.2f}")
print(f"{ratio:.2%}")
print(f"{42:+d}")
print(f"{7:05d}")

Common specifiers include d for integers, .2f for two decimal places, , for thousands separators, .2% for percentages, + for explicit signs, and 05d for zero-padded integers.

Format strings with width, padding, and alignment

text = "Python"
num = 42

print(f"|{text:<10}|")
print(f"|{text:>10}|")
print(f"|{text:^10}|")
print(f"|{num:*>8}|")
print(f"|{num:0=8d}|")

• < left align
• > right align
• ^ center align
• A fill character can appear before the alignment symbol, such as *> or 0=

Python str.format() method

Syntax: "Hello {}".format(name)

str.format() inserts values into {} placeholders and returns the formatted string.

name = "Deepak"
roll = 4359

print("Hello {}, your roll number is {}".format(name, roll))
print("Hello {0}, your roll number is {1}".format(name, roll))
print("Hello {name}, your roll number is {num}".format(name=name, num=roll))

The same format specifiers after the colon work here too: {price:.2f}, {text:<10}, and {num:,}.

Positional and named placeholders with format()

• {} uses argument order from .format()
• {0} and {1} use index positions
• {name} uses keyword arguments

print("{1} before {0}".format("second", "first"))
print("{name} scored {score:.1f}".format(name="Alex", score=88.5))

A missing index raises IndexError. A missing keyword raises KeyError.

f-string vs str.format()

Percent formatting in Python

Percent formatting is old-style formatting. It uses %s, %d, %f, and other placeholders with the % operator. You still see it in older codebases.

Python documents printf-style string formatting. It is not the recommended choice for new code, but it is not removed.

name = "Deepak"
drink = "coffee"
price = 3

message = "Hey %s, this %s costs $%d." % (name, drink, price)
print(message)

What does %d mean in Python?

• %d means signed decimal integer
• %s means string
• %f means floating-point number
• %% prints a literal percent sign

age = 32
text = "Python"
value = 19.99

print("Age: %d" % age)
print("Lang: %s" % text)
print("Price: %.2f" % value)
print("Done 100%%")

Use %d only with integer values.

Common percent formatting placeholders

Format decimal places

Formatting controls display output. It does not change the stored numeric value.

value = 3.14159

print(f"{value:.2f}")
print("{:.2f}".format(value))
print("%.2f" % value)
print(value)

All three formatted outputs show 3.14, while the original variable still holds the full float.

Format percentages

ratio = 0.25

print(f"{ratio:.2%}")
print("{:.2%}".format(ratio))

0.25 displays as 25.00%. Useful for rates, ratios, and progress values.

Format dates and times

Use datetime objects with format codes inside braces:

from datetime import datetime

today = datetime(2026, 6, 23, 15, 30)

print(f"{today:%Y-%m-%d}")
print(f"{today:%d/%m/%Y %H:%M}")
print("{:%Y-%m-%d}".format(today))

See Python datetime for more date and time formatting.

Escape braces in formatted strings

Use double braces when you need literal { or } in the output.

count = 3

print(f"Use {{ and }} to show braces. Count = {count}")
print("Literal braces: {{}}".format())

This avoids confusing the formatter with placeholder syntax.

Which Python string formatting method should you use?

Summary

Use f-strings for most modern Python string formatting. Use str.format() for templates and older compatibility. Use percent formatting mainly when reading or maintaining old code. Use format specifiers for width, alignment, padding, decimals, percentages, and dates. Remember that %d means decimal integer in old percent-style formatting. To split formatted output into fields later, see Python split string.

References

• Python formatted string literals (f-strings)
• Python str.format() documentation
• Python format specification mini-language
• Python printf-style string formatting