Numbers and type conversion

int and float are Python's number types, for whole numbers and for numbers with a decimal point, and int(), float() and str() convert between them and text.

Last updated: 30 Sep, 2026 · Python 3.14

Models are paid for by the amount of text they read and write, so even a program about strings does sums.

Doing arithmetic

price = 499
quantity = 2
print(price * quantity)
print(10 / 4)
print(10 // 4)
print(10 % 4)

998
2.5
2
2

* multiplies. / always gives a float, even when the answer is whole. // divides and drops the part after the decimal point, and % gives what is left over.

Estimating a model's cost

Model providers count text in tokens, pieces of words, and charge a price per thousand or per million of them.

tokens = 1234
price_per_1000 = 0.15
cost = tokens / 1000 * price_per_1000
print(cost)
print(round(cost, 2))

0.1851
0.19

round(cost, 2) keeps two digits after the point, so 0.1851 becomes 0.19. Round a cost before showing it to a person.

Adding to text that looks like a number

A number that arrives from a file, a form or a model often arrives as text. Adding to it fails.

quantity = "2"
print(quantity + 1)

Traceback (most recent call last):
  File "main.py", line 2, in <module>
    print(quantity + 1)
TypeError: can only concatenate str (not "int") to str

The quotes made quantity a string, and Python will not guess whether you meant maths or joining text.

Converting with int(), float() and str()

quantity = "2"
print(int(quantity) + 1)
print(float("0.15") * 2)
print("Total: " + str(998))

3
0.3
Total: 998

int, float and str each turn a value into that type. Text that is not a number cannot become one, and that is a different error:

print(int("two"))

Traceback (most recent call last):
  File "main.py", line 1, in <module>
    print(int("two"))
ValueError: invalid literal for int() with base 10: 'two'

/ vs // vs %

Where numbers show up in AI code

• Counting tokens and estimating what a run costs.
• Settings such as a temperature of 0.2 or a limit of 50 tokens.
• Scores a model gives, which often arrive as text and need float().

Related

• Previous: Strings
• Next: if, elif and else
• Reference: Numeric types in the Python docs