Beginner·16 min·0/47 done

Python Casting

Convert between strings, numbers, and booleans with int(), float(), and str().

Why it matters: Config and model outputs often arrive as strings. Convert them explicitly.

Basics

Casting Functions

Python will not mix strings and numbers for you.

int("12.5") fails. Use int(float("12.5")) instead. Common mistake: forgetting to convert env strings before math.

Tiny example

Convert a string to a float.

raw = "0.2"
temperature = float(raw)
print(temperature)
print(type(temperature))

Basics

bool("False") is True because the string is not empty.

Compare against a set like {"1", "true", "yes"} instead.

Never use eval() on outside input.

Tiny example

Parse a bool from text against a known set.

raw = "false"
print(raw.lower() in {"1", "true", "yes"})

Basics

Floats are approximate. That is binary floating point.

Do not compare floats with ==. Use math.isclose(a, b).

Common mistake: treating float equality as exact.

Tiny example

0.1 + 0.2 is not exactly 0.3.

print(0.1 + 0.2)
print(0.1 + 0.2 == 0.3)

Then AI / ML

Same idea, used in real AI work. Press Try in lab to run it.

AI / ML example

AI / ML: cast config strings

Turn text settings into numbers.

In AI / ML: Temperature and max tokens often start as env strings.

example.py

Python

raw = "0.7"
temperature = float(raw)
max_tokens = int("512")
print(temperature)
print(max_tokens)

AI / ML example 2

AI / ML: bool from text

Do not use bool() on the string False.

In AI / ML: Flags like STREAM often arrive as text, not real booleans.

example.py

Python

raw = "False"
print(bool(raw))
print(raw.lower() in {"1", "true", "yes"})