Type Conversions¶

Python supports conversions between numeric types.

The most common numeric conversions are:

• int() for integers
• float() for floating-point numbers
• complex() for complex numbers

These conversions allow programs to move values between different numeric representations.

flowchart TD
    A[int]
    A --> B[float]
    A --> C[complex]
    B --> D[int]
    B --> C
````

---

## 1. Converting int to float

Converting an integer to a float preserves the numeric value while changing its representation.

```python
x = 5
y = float(x)

print(y)
print(type(y))

Output:

5.0
<class 'float'>

2. Converting float to int¶

Converting a float to an integer truncates toward zero.

x = 3.9
y = int(x)

print(y)

Output:

3

For negative values:

print(int(-3.9))

Output:

-3

3. Converting int to complex¶

An integer can be converted directly to a complex number.

x = 7
z = complex(x)

print(z)

Output:

(7+0j)

4. Converting float to complex¶

A float can also be converted directly.

x = 2.5
z = complex(x)

print(z)

Output:

(2.5+0j)

5. Creating complex numbers from two parts¶

The complex() function can take two arguments:

z = complex(2, 3)
print(z)

Output:

(2+3j)

This means:

[ 2 + 3j ]

6. Converting Strings¶

Strings can often be converted into numeric values.

print(int("42"))
print(float("3.14"))
print(complex("2+3j"))

Output:

42
3.14
(2+3j)

However, the string must be in valid format.

# int("hello")      -> ValueError
# float("abc")      -> ValueError

7. Implicit Numeric Promotion¶

Python also performs automatic promotion during mixed arithmetic.

print(type(3 + 2.5))
print(type(3 + 2j))
print(type(2.5 + 2j))

Output:

<class 'float'>
<class 'complex'>
<class 'complex'>

This follows the general widening order:

int -> float -> complex

flowchart LR
    A[int] --> B[float] --> C[complex]

8. Worked Examples¶

Example 1: integer to float¶

x = 10
print(float(x))

Example 2: float to integer¶

y = 8.99
print(int(y))

Example 3: integer to complex¶

n = 4
print(complex(n))

9. Common Pitfalls¶

Assuming float-to-int rounds¶

print(int(4.9))

This produces 4, not 5.

Forgetting complex string syntax¶

complex("2+3j")

works, but malformed strings do not.

Ignoring promotion¶

Mixed arithmetic can produce wider numeric types than expected.

10. Summary¶

Key ideas:

• Python supports explicit conversion with int(), float(), and complex()
• float-to-int conversion truncates toward zero
• integers and floats can be converted into complex numbers
• strings may be converted when properly formatted
• mixed numeric arithmetic promotes values from int to float to complex

Type conversion is essential for writing programs that combine different numeric representations safely and clearly.