Type conversion #

Let's try something new: find out the length of a number the same way you found out the length of your name. Enter len(304023) and press Enter:

>>> len(304023)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: object of type 'int' has no len()

You have encountered an error! It says that objects of type 'int' (short for 'integer', a whole number) do not have a length. What can you do now? Maybe you can try writing the number as a string? Strings have length, right?

>>> len("304023")
6

But it can also be done without quotation marks. There is also a function that converts a number to a string. It's called str.

>>> str(304023)
"304023"
>>> len(str(304023))
6

When entering a number directly, it will probably be more pleasant to use quotation marks. However, the str function will become more useful when you want to leave the calculation of the number to Python.

>>> str(304023 * 12345 * 83845)
'314684030130075'
>>> len(str(304023 * 12345 * 83845))
15

Similarly to str converting to strings, the int function converts things to integers.

>>> int("304023")
304023

The number can always be converted to text, but the opposite is not always possible. What happens when you try to convert a string without digits - for example, 'hello'?

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