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Python abs(): Absolute Value Function Explained

The built-in abs() function returns the absolute value of a number. It supports integers, floats, and complex numbers, and works with custom numeric types that implement __abs__(). This guide covers syntax, examples, performance notes, error handling, and real-world use cases to help you apply abs() effectively.

Syntax

abs(x)

Parameter: A numeric value such as int, float, complex, or an object implementing __abs__().

Returns: The absolute value of x. For integers and floats, returns the same type; for complex numbers, returns a float magnitude.

Quick examples

print(abs(-10))     # 10
print(abs(3.14))    # 3.14
print(abs(0))       # 0
print(abs(-0.0))    # 0.0

Complex numbers

For complex inputs, abs() returns the modulus, computed as sqrt(real**2 + imag**2).

z = 3 + 4j
print(abs(z))       # 5.0

Custom numeric types

Implement __abs__() to define absolute value behavior for your class.

class Distance:
    def __init__(self, x):
        self.x = x
    def __abs__(self):
        return self.x if self.x >= 0 else -self.x

d = Distance(-7)
print(abs(d))       # 7

Practical use cases

• Error and deviation: Measure differences without sign.
• Sorting by magnitude: Use as a key for consistent ordering.
• Numerical stability: Compare magnitudes in algorithms.

nums = [-3, -1, 2, 5]
print(sorted(nums, key=abs))  # [-1, 2, -3, 5]

Common errors and caveats

• Non-numeric types: Passing a string or list raises TypeError.
• Large integers: Python integers are arbitrary precision; no overflow occurs.
• Floating point: Beware of rounding errors; extremely small values may approach zero.

try:
    print(abs("10"))
except TypeError as e:
    print(e)  # bad operand type for abs(): 'str'

Performance and alternatives

• Single values: Built-in abs() is implemented in C and is very fast.
• Arrays: Use numpy.abs for vectorized numerical data.
• Conditional equivalence: x if x >= 0 else -x is equivalent but less clear; prefer abs().

FAQ

Does abs() handle negative zero?

Yes. abs(-0.0) returns 0.0.

What does abs() return for complex numbers?

A float representing the magnitude of the complex number.

Can I use abs() with custom objects?

Yes, if the object implements __abs__().

Related keywords

Python abs, absolute value, complex modulus, TypeError, numerical stability, numpy.abs, sorting key, floating point

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