int Type Conversion¶

Python provides the int() function to convert values into integers.

This is one of the most common type conversions in Python, especially when working with:

• user input
• strings containing digits
• floating-point values
• boolean values

flowchart TD
    A[value]
    A --> B[int()]
    B --> C[integer result]
````

---

## 1. Basic Syntax

```python
int(x)

The function attempts to convert x into an integer.

Example:

print(int("42"))
print(int(3.9))
print(int(True))

Output:

42
3
1

2. Converting from Strings¶

A string containing digits can be converted to an integer.

x = "123"
y = int(x)

print(y)
print(type(y))

Output:

123
<class 'int'>

Negative numbers¶

print(int("-25"))

Output:

-25

3. Converting from Floats¶

When converting a float to an integer, Python truncates toward zero.

print(int(3.9))
print(int(3.1))
print(int(-3.9))

Output:

3
3
-3

This is not rounding. It is truncation.

flowchart LR
    A[3.9] --> B[int()] --> C[3]
    D[-3.9] --> E[int()] --> F[-3]

4. Converting from Booleans¶

Because bool is a subclass of int, Boolean values convert naturally.

print(int(True))
print(int(False))

Output:

1
0

5. Base Conversion from Strings¶

int() can also interpret strings written in different bases.

Syntax:

int(string, base)

Example:

print(int("1010", 2))
print(int("52", 8))
print(int("2A", 16))

Output:

10
42
42

This is useful when reading binary, octal, or hexadecimal values.

6. Invalid Conversions¶

Some conversions fail and raise ValueError.

int("hello")
int("3.14")

These fail because the strings do not represent valid integers in base 10.

Example:

try:
    print(int("hello"))
except ValueError:
    print("Cannot convert")

7. User Input Pattern¶

A common pattern is converting input strings into integers.

age = int(input("Enter your age: "))
print(age + 1)

This works because input() always returns a string.

8. Worked Examples¶

Example 1: converting input¶

text = "45"
number = int(text)

print(number * 2)

Output:

90

Example 2: converting a float¶

price = 19.99
whole = int(price)

print(whole)

Output:

19

Example 3: binary string to integer¶

bits = "1101"
value = int(bits, 2)

print(value)

Output:

13

9. Common Pitfalls¶

Assuming int() rounds¶

print(int(3.9))

This gives 3, not 4.

Forgetting base when needed¶

int("1010")

This is interpreted as decimal 1010, not binary 10.

10. Summary¶

Key ideas:

• int() converts compatible values into integers
• float conversion truncates toward zero
• strings can be converted when they contain valid integer text
• int(string, base) supports other number bases
• invalid conversions raise ValueError

Understanding int() is essential for handling input and performing exact numeric operations.