# Python int function – Ultimate Guide

Posted by Marta on August 6, 2020 Viewed 113 times

In this tutorial I will share how the int() function works in python, the purpose of the function, different parameter types the function accepts In this tutorial I will share how the int() function works in python, the purpose of the function, different parameter types the function accepts. I will also share example which make the function fails and some use cases where this function is really useful.

The int() function will return an integer constructed from a number or a string. If you pass no arguments, the function will return 0

This function accepts two argument, first the number to convert and second the base of the previous number. If no base is passed, the default base is 10.

```number_text="4"
number = int(number_text)
print(type(number))
print(number)```

Output:

```<class 'int'>
4```

If you like to use a custom base, the first parameter should be a string, bytes or byte array type. See the example below:

```number_base16 = int('17',16)
print(number_base16)

number_base3 = int('3',4)
print(number_base3)```

Output:

```23
3```

Otherwise, if you passed a float as first parameter and try to convert it to an integer with an specific base for instance base 16, you will get the following error:

```number_base16 = int(17.5,16)
print(number_base16)```

Output:

```Traceback (most recent call last):
File line 1, in <module>
number_base16 = int(17.5,16)
TypeError: int() can't convert non-string with explicit base```

### Example #1: Convert string to int

```number_text="1234" # number saved in text
number = int(number_text)
print(type(number))
print(number)```

Output

```<class 'int'>
1234```

### Example #2: Convert float to int

```float_var = 4.3
int_num = int(float_var)
print(int_num)```

Output:

`4`

Keep in mind the int function doesn’t do any rounding, it will just remove the decimal part.

## Python int variable size

Since Python 3 there is no limit to the value of integers( Check out the Documentation) . However there is the constant `sys.maxsize`, value 9223372036854775807 (9,223,372,036,854,775,807) which can be used as an integer, larger than any practical list or string index. That means that `sys.maxsize` is the maximum a collection index can handle, therefore the maximum number of items the collection can hold.a list See the example below:

```import sys
print(sys.maxsize)```

Output:

`9223372036854775807`

## Python int function exercises and solutions

So far we have seen how to use int function and the different parameters the function accepts. Next I will share some exercises where the int function is necessary.

### Example #1

First exercise is reading a number entered by the user, and return the absolute number. See the code below:

```num = input('Enter a number:')
abs_value = abs(int(num))
print('Absolute Value: '+ str(abs_value))```

Explanation:

In line 1 will read the number entered by the user. This number is a string. Next line will convert the string to an absolute value. Since the `abs()` function only accepts numbers, I need to use the `int()` function and convert the `num` variable to number.

### Example #2

Another exercise exercise is reading two numbers from the user and return the result of adding the two numbers. The code below illustrates how to achieve that:

```num1 = input('Enter a number:')
num1 = int(num1)
num2 = input('Enter a number:')
num2 = int(num2)
print('Result: ' + str(num1 + num2))```

In this example above the `int()` function is used to convert a string to an integer in line 2 and line 4. The `num1` and `num2` variables need to be converted to integers before the addition can be calculated.

## Python int function rounding

The int function will round the number to the whole part toward zero. It will leave the whole part and truncate the decimal part

```float1_var = 4.6
print(int(float1_var))```

Output:

`4`

## Frequent errors

### ValueError: invalid literal for int() with base 10

What if you pass to the function something that is not convertible to a number, for instance a character. The function will return the ValueError: invalid literal for int() with base 10, which indicates the parameter passed to the function is not a base 10 number. See an example below:

`number1 = int('q')`

Output:

```Traceback (most recent call last):
File line 1, in <module>
number1 = int('q')
ValueError: invalid literal for int() with base 10: 'q'```

## Conclusion

To summarise, this article covers how to use the int() function, a few examples of how to use it and frequent errors to avoid. I hope this tutorial was useful and thank you for reading and supporting the this blog.

Happy Coding!!

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