float() in Python

In Python, the float() function is used to convert numbers or numeric strings into floating-point numbers. A floating-point number is simply a number with a decimal point (for example, 3.14, -0.5, or 10.0). This function is especially useful when dealing with user input or when precise decimal calculations are needed.

Example:

Input: 10
Output: 10.0

Syntax

float() function in Python has following syntax:

float(x)

Parameter: x (optional) can be a number (integer or float), a string representing a number, like "10.5" or "inf", "infinity" or "nan".

Return Value:

• Returns a floating-point number corresponding to x.
• If no argument is passed, it returns 0.0.
• If a string does not represent a valid number, it raises a ValueError.
• If a number is too large, it raises an OverflowError.

Converting Integers to Float

One can easily turn an integer into a float by wrapping it with float().

Example: In this example, we passed an integer type value to the float() function.

number = 90
result = float(number)
print(result)

90.0

Converting Strings to Float

If a string contains numeric values, float() can convert it into a floating-point number.

Example: This code converts numeric strings (both integer-like and decimal-like) into floats.

string = "90"  # String representing an integer
result1 = float(string)

float_string = "-16.54"  # String representing a float
result2 = float(float_string)

print(result1)
print(result2)

90.0
-16.54

Infinity and Nan

Python allows infinite and undefined numbers using float().

Example: In this example, we passed infinite and NaN values to float() function and then print their equivalent float values.

print(float("inf"))  # Infinity
print(float("infinity"))

print(float("nan"))  # Not-a-Number
print(float("NaN"))

inf
inf
nan
nan

Explanation:

• "inf" or "infinity": represents positive infinity.
• "-inf": represents negative infinity.
• "nan" (Not a Number): represents undefined values, like results of invalid math operations.
• These strings are case-insensitive

Exceptions and Errors

Sometimes the float() function in Python may not be compatible with all the datatypes. In this case, it may raise an exception or generate an error.

1. ValueError

Python float() will raise ValueError if the passed parameter is not a numeric value.

Example: In this example, we passed an alphabet string as a parameter to float() function.

number = "geeks"
try:
    print(float(number))
except ValueError as e:
    print(e)

could not convert string to float: 'geeks'

2. OverflowError

float() in Python will raise OverflowError if the passed parameter is too large.

Example: This code raises an OverflowError because 10**309 exceeds Python’s floating-point range.

print(float(10**309))

Output

Traceback (most recent call last):
File "/home/1eb6a2abffa536ccb1cae660db04a162.py", line 1, in <module>
print(float(10**309))
OverflowError: int too large to convert to float