Python How to Convert Float to Int Without Rounding

To convert a float to an int without rounding in Python, use int(your_float) or math.trunc(your_float), which simply remove the decimal part without rounding.

Examples

Input3.7

Output3

Input-2.9

Output-2

Input5.0

Output5

How to Think About It

To convert a float to an int without rounding, think about removing the decimal part completely instead of changing the number up or down. Using int() or math.trunc() cuts off everything after the decimal point, keeping only the whole number part.

Algorithm

1

Get the float number as input.

2

Remove the decimal part without rounding by truncating it.

3

Return the resulting integer.

Code

python

import math

float_num = 3.7
int_num = int(float_num)  # or use math.trunc(float_num)
print(int_num)

Output

3

Dry Run

Let's trace converting 3.7 to int without rounding.

1

Input float

float_num = 3.7

2

Convert using int()

int_num = int(3.7) which becomes 3

3

Print result

Output is 3

Step	Value
Input float	3.7
After int()	3
Output	3

Why This Works

Step 1: int() truncates decimals

The int() function removes the decimal part of a float without rounding, simply keeping the integer portion.

Step 2: math.trunc() does the same

The math.trunc() function also truncates the decimal part and returns the integer part, useful for clarity.

Alternative Approaches

Using math.trunc()

python

import math
float_num = 3.7
int_num = math.trunc(float_num)
print(int_num)

Explicitly shows truncation, good for readability.

Using string split

python

float_num = 3.7
int_num = int(str(float_num).split('.')[0])
print(int_num)

Converts float to string and splits at decimal, less efficient but shows manual truncation.

Complexity: O(1) time, O(1) space

Time Complexity

Conversion using int() or math.trunc() is a constant time operation, O(1), as it only processes one number.

Space Complexity

No extra memory is needed beyond storing the input and output, so space complexity is O(1).

Which Approach is Fastest?

int() is the fastest and simplest method; math.trunc() is equally fast but more explicit; string splitting is slower and less efficient.

Approach	Time	Space	Best For
int()	O(1)	O(1)	Simple and fast truncation
math.trunc()	O(1)	O(1)	Explicit truncation with math module
String split	O(n)	O(n)	Manual truncation, less efficient