freeCodeCamp/guide/english/python/how-to-convert-strings-into-integers-in-python/index.md

title
How to Convert Strings into Integers in Python

How to Convert Strings into Integers in Python

Just like the str() built-in, Python also offers a handy built-in which takes a string object as an argument and returns the corresponding integer object.

Example Usage:

# Here age is a string object
age = "18"
print(age)
# Converting string to integer
int_age = int(age)
print(int_age)

Output

18
18

Here although the output is visually similar but you should keep in mind that the first line prints a string object while the line next to it prints a integer object which is further illustrated in the next example:

age = "18"
print(age+2)

Output:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: cannot concatenate 'str' and 'int' objects

The error should make it clear to you that you need to convert the age object to an integer before adding something to it.

age = "18"
age_int = int(age)
print(age_int+2)

Output:

20

But you should keep in mind some special cases:

1. A floating point(an integer with fractional part) as an argument will return the float rounded down to the nearest whole integer. For example : print(int(7.9)) will print 7. Also print(int("7.9")) will result an error since the string is an invalid argument to convert to an integer.

   Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    ValueError: invalid literal for int() with base 10: '7.9'
   

2. Also any integer in words if given as an argument will return the same error as above: print(int("one")) will give an error as follows:

   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
   ValueError: invalid literal for int() with base 10: 'one'
   

More Information:

Official documentation for int() built-in can be found here