Python ValueError Exception Handling Examples

Filed Under: Python
Python ValueError

1. What is Python ValueError?

Python ValueError is raised when a function receives an argument of the correct type but an inappropriate value. Also, the situation should not be described by a more precise exception such as IndexError.

2. ValueError Example

You will get ValueError with mathematical operations, such as square root of a negative number.


>>> import math
>>> 
>>> math.sqrt(-10)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: math domain error
>>> 

3. Handling ValueError Exception

Here is a simple example to handle ValueError exception using try-except block.


import math

x = int(input('Please enter a positive number:\n'))

try:
    print(f'Square Root of {x} is {math.sqrt(x)}')
except ValueError as ve:
    print(f'You entered {x}, which is not a positive number.')

Here is the output of the program with different types of input.


Please enter a positive number:
16
Square Root of 16 is 4.0

Please enter a positive number:
-10
You entered -10, which is not a positive number.

Please enter a positive number:
abc
Traceback (most recent call last):
  File "/Users/pankaj/Documents/PycharmProjects/hello-world/journaldev/errors/valueerror_examples.py", line 11, in <module>
    x = int(input('Please enter a positive number:\n'))
ValueError: invalid literal for int() with base 10: 'abc'

Our program can raise ValueError in int() and math.sqrt() functions. So, we can create a nested try-except block to handle both of them. Here is the updated snippet to take care of all the ValueError scenarios.


import math

try:
    x = int(input('Please enter a positive number:\n'))
    try:
        print(f'Square Root of {x} is {math.sqrt(x)}')
    except ValueError as ve:
        print(f'You entered {x}, which is not a positive number.')
except ValueError as ve:
    print('You are supposed to enter positive number.')

4. Raising ValueError in a function

Here is a simple example where we are raising ValueError for input argument of correct type but inappropriate value.


import math


def num_stats(x):
    if x is not int:
        raise TypeError('Work with Numbers Only')
    if x < 0:
        raise ValueError('Work with Positive Numbers Only')

    print(f'{x} square is {x * x}')
    print(f'{x} square root is {math.sqrt(x)}')

5. References

Comments

  1. Jemoh says:

    Wow!! You codes are simple hence easy to understand.. they are really fun to type…thanks

Comments are closed.

close
Generic selectors
Exact matches only
Search in title
Search in content
Post Type Selectors