float()

float(x=0.0)

The float() function converts a number or a string representing a number to a floating-point number. It’s one of Python’s fundamental type conversion functions, essential for any numerical computation involving decimals.

Syntax

float(x=0.0)

Parameters

Parameter	Type	Default	Description
x	int, float, or str	0.0	The value to convert to a float. Can be an integer, another float, or a string representation of a number.

Examples

Converting integers to floats

# Converting integers to floats
print(float(10))      # 10.0
print(float(-5))      # -5.0
print(float(0))       # 0.0

Converting strings to floats

# Converting numeric strings to floats
print(float("3.14"))      # 3.14
print(float("-2.5"))      # -2.5
print(float("0.0"))       # 0.0

# String with whitespace (stripped automatically)
print(float("  42.5  "))  # 42.5

Special string values

# Special string values
print(float("inf"))       # inf
print(float("infinity"))  # inf
print(float("-inf"))      # -inf
print(float("nan"))        # nan

Working with floats directly

# Passing a float returns the same value
print(float(3.14))    # 3.14
print(float(-2.5))    # -2.5
print(float(0.0))     # 0.0

Common Patterns

User input processing

# Converting user input to float for calculations
price = float(input("Enter price: "))
tax = price * 0.08
print(f"Total: {price + tax}")

Default values

# Using float() for default numeric values
def calculate_area(radius, pi=3.14159):
    return pi * (radius ** 2)

# Using float() to ensure float division
result = float(10) / 3  # 3.3333333333333335

Numerical computations

# Precision calculations
a = float("0.1")
b = float("0.2")
print(a + b)  # 0.30000000000000004 (floating-point precision)

# Scientific notation
print(float("1e-5"))  # 1e-05 (0.00001)
print(float("2.5e3")) # 2500.0

Errors

ValueError

float() raises a ValueError when given a non-numeric string:

# These will raise ValueError
float("hello")     # ValueError: could not convert string to float: 'hello'
float("3.14.15")   # ValueError: could not convert string to float: '3.14.15'
float("")          # ValueError: could not convert string to float: ''
float("2 + 3")     # ValueError: could not convert string to float: '2 + 3'

TypeError

float() raises a TypeError for unsupported types:

# These will raise TypeError
float([1, 2, 3])    # TypeError: can't convert 'list' object to float
float({"a": 1})     # TypeError: can't convert 'dict' object to float
float(None)         # TypeError: can't convert 'NoneType' object to float

See Also

• built-in::int — Convert to integer
• str::str — Convert to string
• built-in::complex — Create a complex number