Python float() Function

Parameter	Description
`x` optional	A number or a string such as `"3.14"`, `"1e-3"` or `"inf"`. Default: `0.0`

Parameter

Description

x optional

A number or a string such as "3.14", "1e-3" or "inf". Default: 0.0

Examples

Convert strings and numbersTry it yourself

print(float("3.14"), float(" 42 "), float(7))
print(float("1_000.5"))
print(float("inf") > 10 ** 100)

Output

3.14 42.0 7.0
1000.5
True

Floating-point roundingTry it yourself

print(0.1 + 0.2)
print(round(0.1 + 0.2, 2))
print(abs((0.1 + 0.2) - 0.3) < 1e-9)

Output

0.30000000000000004
0.3
True

Handle bad inputTry it yourself

for text in ["12.5", "abc"]:
    try:
        print(float(text))
    except ValueError:
        print(f"not a number: {text!r}")

Output

12.5
not a number: 'abc'

Common mistakes

Floats are binary approximations: 0.1 + 0.2 is 0.30000000000000004. Compare with a tolerance (math.isclose()), and use decimal.Decimal for money.
float("1,5") fails: commas aren't decimal separators. Replace them first or use locale.

Version	Change
Python 3.0	Added
Python 3.6	Underscores are allowed in numeric strings, e.g. `"1_000.5"`.
Python 3.14	Added the `float.from_number()` class method.

Version

Change

Added

Underscores are allowed in numeric strings, e.g. "1_000.5".

Added the float.from_number() class method.

int() · Convert a number or string to an integer. Floats are truncated toward zero, and strings can be in any base from 2 to 36.

round() · Round a number to a given number of decimal places. Halfway values round to the nearest even number (banker's rounding).

complex() · Create a complex number from a real and an imaginary part, or parse one from a string such as '1+2j'.

str() · Convert a value to its readable text form, or decode bytes into a string. Strings are immutable sequences of characters.