Python abs() Function

The abs() function returns the absolute value of a number. The absolute value represents the distance from zero, so a negative number becomes positive while positive numbers remain unchanged.

Syntax

abs(number)

1. Basic Example

number = -10

result = abs(number)

print(result)

Output:

10

2. Positive Number

number = 25

print(abs(number))

Output:

25

A positive number remains unchanged.

3. Zero

number = 0

print(abs(number))

Output:

0

4. Negative Numbers

numbers = [-10, -20, -5, -30]

for number in numbers:
    print(abs(number))

Output:

10
20
5
30

5. Calculate Distance Between Two Numbers

abs() is very useful for calculating the distance between two values.

a = 10 b = 25

distance = abs(a - b)

print(distance)

Output:

15

The calculation is:

25 - 10 = 15

Even if the order is reversed:

a = 25 b = 10

distance = abs(a - b)

print(distance)

Output:

15

6. Distance from Zero

numbers = [-15, -8, 0, 12, 20]

for number in numbers:
    print(
        number,
        abs(number)
    )

Output:

-15 15
-8 8
0 0
12 12
20 20

7. abs() with min()

You can use abs() as the key for min().

numbers = [-10, 5, -3, 8, -1]

result = min(
    numbers,
    key=abs
)

print(result)

Output:

-1

Python compares:

-10 → 10
5   → 5
-3  → 3
8   → 8
-1  → 1

Therefore, -1 is closest to zero.

8. abs() with max()

numbers = [-10, 5, -3, 8, -1]

result = max(
    numbers,
    key=abs
)

print(result)

Output:

-10

The absolute values are:

10, 5, 3, 8, 1

So -10 has the largest absolute value.

9. abs() with sorted()

You can sort numbers according to their distance from zero.

numbers = [-10, 5, -3, 8, -1]

result = sorted(
    numbers,
    key=abs
)

print(result)

Output:

[-1, -3, 5, 8, -10]

The sorting is based on:

1, 3, 5, 8, 10

10. Sort by Absolute Value in Descending Order

numbers = [-10, 5, -3, 8, -1]

result = sorted(
    numbers,
    key=abs,
    reverse=True
)

print(result)

Output:

[-10, 8, 5, -3, -1]

11. abs() with map()

Since you already learned map(), you can use abs() directly as the function.

numbers = [-10, -20, 5, -8]

result = map(abs, numbers)

print(list(result))

Output:

[10, 20, 5, 8]

This is simpler than using a lambda:

map(lambda x: abs(x), numbers)

You can directly write:

map(abs, numbers)

12. abs() with filter()

Suppose we want numbers whose absolute value is greater than 10.

numbers = [-20, -5, 8, 15, 3, -30]

result = filter(
    lambda x: abs(x) > 10,
    numbers
)

print(list(result))

Output:

[-20, 15, -30]

The absolute values are:

20, 5, 8, 15, 3, 30

Only values greater than 10 are selected.

13. Find Numbers Close to Zero

numbers = [-10, 3, -2, 8, 1, -5]

result = [
    x
    for x in numbers
    if abs(x) <= 3
]

print(result)

Output:

[3, -2, 1]

14. Find Difference Within a Limit

a = 100 b = 105

if abs(a - b) <= 5:
    print("Values are close")
else:
    print("Values are far apart")

Output:

Values are close

This pattern is useful when comparing numerical values.

15. Compare Temperature Changes

yesterday = 25 today = 30

change = abs(today - yesterday)

print("Temperature change:", change)

Output:

Temperature change: 5

16. Find Closest Number to a Target

Suppose the target is 50.

numbers = [20, 45, 55, 70, 90]

target = 50

closest = min(
    numbers,
    key=lambda x: abs(x - target)
)

print(closest)

Output:

45

Why?

20 → |20 - 50| = 30
45 → |45 - 50| = 5
55 → |55 - 50| = 5
70 → |70 - 50| = 20
90 → |90 - 50| = 40

Both 45 and 55 are equally close. Python returns the first one encountered.

17. Find Closest Course Price

prices = [10000, 15000, 20000, 25000, 30000]

target = 18000

closest = min(
    prices,
    key=lambda price: abs(price - target)
)

print(closest)

Output:

20000

The difference is:

|20000 - 18000| = 2000

18. Find Closest Student Mark

marks = [55, 65, 72, 80, 90]

target = 75

closest = min(
    marks,
    key=lambda mark: abs(mark - target)
)

print(closest)

Output:

72

Because:

|72 - 75| = 3
|80 - 75| = 5

So 72 is closer.

19. abs() with Decimal Values

abs() also works with floating-point numbers.

number = -12.75

print(abs(number))

Output:

12.75

20. abs() with Complex Numbers

abs() can also calculate the magnitude of a complex number.

number = 3 + 4j

print(abs(number))

Output:

5.0

This is calculated using:

√(3² + 4²) = √25 = 5

21. Practical Example : Profit and Loss

Suppose a business has revenue and cost.

revenue = 50000 cost = 65000

difference = revenue - cost

print("Difference:", abs(difference))

Output:

Difference: 15000

The actual difference is:

50000 - 65000 = -15000

abs() gives the size of the difference:

15000

22. Practical Example : Attendance Difference

expected = 100 actual = 85

difference = abs(expected - actual)

print("Difference:", difference)

Output:

Difference: 15

23. Practical Example : Data Analysis

Suppose we have actual and predicted values.

actual = 100 predicted = 92

error = abs(actual - predicted)

print("Absolute Error:", error)

Output:

Absolute Error: 8

This concept is important in data science and machine learning, where absolute error is used to measure the difference between actual and predicted values.

24. Calculate Total Absolute Error

actual = [100, 200, 300, 400]
predicted = [90, 210, 280, 390]

errors = [
    abs(a - p)
    for a, p in zip(actual, predicted)
]

total_error = sum(errors)

print("Errors:", errors)
print("Total Error:", total_error)

Output:

Errors: [10, 10, 20, 10]
Total Error: 50

This combines:

abs()
zip()
list comprehension
sum()

25. Calculate Mean Absolute Error

Mean Absolute Error (MAE) is commonly used in machine learning.

actual = [100, 200, 300, 400]
predicted = [90, 210, 280, 390]

errors = [
    abs(a - p)
    for a, p in zip(actual, predicted)
]

mae = sum(errors) / len(errors)

print("MAE:", mae)

Output:

MAE: 12.5

26. Important Difference

Remember that abs() does not sort or modify a collection.

number = -25

print(abs(number))

It simply returns the absolute value:

25

Easy way to remember

abs(-10) → 10
abs(10)  → 10
abs(0)   → 0