float() in Python

Difficulty Level : Easy
Last Updated : 17 Nov, 2017

The float() method is used to return a floating point number from a number or a string.
Syntax:

float(x)

The method only accepts one parameter and that is also optional to use. Let us look at the various types of argument, the method accepts:

A number : Can be an Integer or a floating point number.
A String :
- Must contain numbers of any type.
- Any left or right whitespaces or a new line is ignored by the method.
- Mathematical Operators can be used.
- Can contain NaN, Infinity or inf (any cases)

Values that the float() method can return depending upon the argument passed

If an argument is passed, then the equivalent floating point number is returned.
If no argument is passed then the method returns 0.0 .
If any string is passed that is not a decimal point number or does not match to any cases mentioned above then an error will be raised.
If a number is passed outside the range of Python float then OverflowError is generated.

Now let us look at various examples and the working of float() method.

# Python program to illustrate
# Various examples and working of float()
# for integers
print(float(21.89))
  
# for floating point numbers
print(float(8))
  
# for integer type strings
print(float("23"))
  
# for floating type strings
print(float("-16.54"))
  
# for string floats with whitespaces
print(float("     -24.45   \n"))
  
# for inf/infinity
print(float("InF"))
print(float("InFiNiTy"))
  
# for NaN
print(float("nan"))
print(float("NaN"))
  
# Error is generated at last
print(float("Geeks"))

Output:

21.89
8.0
23.0
-16.54
-24.45
inf
inf
nan
nan

All lines are executed properly but the last one which will return an error:

Traceback (most recent call last):
  File "/home/21499f1e9ca207f0052f13d64cb6be31.py", line 25, in 
    print(float("Geeks"))
ValueError: could not convert string to float: 'Geeks'

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