Summary  
This chapter explains how to convert values between core Python types—using int(), float(), str(), and bool()—while highlighting valid conversions, truthiness rules, and common pitfalls. It also covers best practices for safely validating and handling errors during conversion.

General domain of usage  
User input processing

Type conversion lets you move between core Python types so values can be compared, calculated, or displayed.

Watch this video to see practical examples of type conversion in Python, including how to safely convert between `int`, `float`, `str`, and `bool`. Learn common pitfalls and best practices for handling user input and data transformation.

## Converting to `int`

`int(x)` makes an integer.

* **From an int**: returns the same number;
* **From a float**: truncates toward zero (for example, `int(2.9)` returns `2`, `int(-2.9)` returns `-2`);
* **From a string**: the string must represent an integer (optional spaces and sign are ok).

### Valid Conversions

age_input = " 42 "
print(int(age_input))      # 42
print(int(2.9))            # 2
print(int(-2.9))           # -2
print(int("7"))            # 7
print(int(" -15 "))        # -15

int("2.5")        # ValueError - not an integer string
int("42a")        # ValueError

## Converting to `float`

`float(x)` makes a floating-point number.

* Works for ints and decimal or scientific-notation strings;
* Commas are not decimal points in Python.

### Valid conversions

print(float(3))            # 3.0
print(float("2.5"))        # 2.5
print(float("1e3"))        # 1000.0

float("2,5")   # ValueError - use a dot, not a comma

## Converting to `str`

`str(x)` makes a human-readable string representation. Prefer f-strings when you are building messages.

print(str(42))             # "42"
print(str(3.5))            # "3.5"
print(f"Ada scored {98} points.")

## Converting to `bool`

`bool(x)` follows Python truthiness rules.

* **Numbers**: `0` is `False`, any other number is `True`;
* **Strings**: `""` (empty) is `False`, any non-empty string is `True` (even `"0"` and `"False"`).


print(bool(0))             # False
print(bool(7))             # True
print(bool(""))            # False
print(bool("0"))           # True
print(bool("False"))       # True

## Mistakes to Avoid

* `int("2.5")` raises `ValueError` - parse as `float()` first, then truncate or round;
* Locale habit: `"2,5"` is invalid - use `"2.5"`;
* Underscores in input strings: `"1_000"` is invalid - remove underscores first: `"1_000".replace("_", "")`;
* Truthiness surprise: `bool("0")` is `True` - compare string contents explicitly if needed, for example `s == "0"`.

A focused, beginner-friendly course on working with numbers in Python. Learn about integers, floats, arithmetic operations, type conversion, and how to avoid common pitfalls when handling numerical data.

Type Conversion Essentials

Converting to `int`

Valid Conversions

These Raise ValueError

Converting to `float`

Valid conversions

These Raise ValueError

Converting to `str`

Converting to `bool`

Mistakes to Avoid

1. Which call raises a `ValueError`?

2. Pick the correct statement.

Type Conversion Essentials

Converting to int

Valid Conversions

These Raise ValueError

Converting to float

Valid conversions

These Raise ValueError

Converting to str

Converting to bool

Mistakes to Avoid

1. Which call raises a ValueError?

2. Pick the correct statement.

Converting to `int`

Converting to `float`

Converting to `str`

Converting to `bool`

1. Which call raises a `ValueError`?