5 Best Ways to Get the Machine Limits Information for Float With Instances in Python

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πŸ’‘ Problem Formulation: When working with floating-point numbers in Python, developers often need to know the limits of these numbers, such as the maximum, minimum, and precision level that the host machine can accurately handle. For example, understanding the difference between the largest representable float or the smallest positive number that is not zero can be crucial in avoiding overflow or underflow errors in computational tasks.

Method 1: Using the sys Module

The sys module in Python contains system-specific parameters and functions, one of which includes the float_info object. This provides the necessary information about the limits of floating-point numbers, such as their maximum, minimum, and epsilon values which dictate precision.

Here’s an example:

import sys



sys.float_info(max=1.7976931348623157e+308, max_exp=1024, max_10_exp=308, min=2.2250738585072014e-308, min_exp=-1021, min_10_exp=-307, dig=15, mant_dig=53, epsilon=2.220446049250313e-16, radix=2, rounds=1)

This code snippet imports the sys module and prints out the float_info data structure. It provides a wealth of information, such as the maximum value a float can have, the smallest positive representable number, and the approximate precision in decimal digits, among others.

Method 2: Using the numpy Module

The numpy module offers an API designed for mathematical operations and can also be used to obtain machine limits for NumPy float types. Numpy’s finfo function provides a detailed float machine limits report suitable for various float types provided by NumPy, extending the basic support in Python to include types like numpy.float32 or numpy.float64.

Here’s an example:

import numpy as np



Machine parameters for float64
precision =  15   resolution =  1e-15
machep =  -52   eps =        2.220446049250313e-16
negep =   -53   epsneg =     1.1102230246251565e-16
minexp = -1022   tiny =      2.2250738585072014e-308
maxexp =  1024   max =       1.7976931348623157e+308
nexp =     11    min =       -max
smallest_normal = 2.2250738585072014e-308   smallest_subnormal = 4.9406564584124654e-324

This snippet uses the numpy module to print the floating-point number limits for the np.float64 data type. The finfo function is there to provide detailed limits which include minimum and maximum values, epsilon, and precision among other valuable bits of information.

Method 3: Using the decimal Module

The Python decimal module provides support for fast correctly-rounded decimal floating-point arithmetic. It offers the getcontext() method to view and modify the context for decimal operations which includes precision, rounding option, and flags for understanding the float limitations within the decimal precision.

Here’s an example:

from decimal import getcontext

context = getcontext()


Context(prec=28, rounding=ROUND_HALF_EVEN, Emin=-999999, Emax=999999, capitals=1, clamp=0, flags=[], traps=[InvalidOperation, DivisionByZero, Overflow])

This code displays the current context for decimal operations, which includes the precision (number of decimal digits), rounding mechanism, and the range of exponents (Emin and Emax), among others. The context helps in understanding how decimals would behave in precision-critical computations.

Method 4: Using the mpmath Module

For high-precision arithmetic, one can use the mpmath library in Python, which allows for arbitrary-precision floating-point arithmetic. The mp object from the mpmath module can be used to get or set the working precision and limits for large or small numbers, which is vital for very high precision calculations.

Here’s an example:

from mpmath import mp



Mpmath settings:
  mp.prec = 53                [default: 53]
  mp.dps = 15                 [default: 15]
  mp.trap_complex = False     [default: False]

In this code, we import the mp object from the mpmath module and print its properties which include precision and decimal places. This is extremely useful for developers that need to perform calculations that require more precision than what’s provided natively by Python’s float.

Bonus One-Liner Method 5: Using float’s __repr__ method

For a quick and dirty way to get a glimpse into the machine’s float representation, one might simply look at the default string representation of Python’s float type, which, while not exhaustive, provides instant access to the rounded display of numbers.

Here’s an example:




This snippet uses the __repr__ method, specifically the hex() method, of a float to print its hexadecimal representation. This is a somewhat less common but still valid method to get an idea of how the system represents float values at a low level.


  • Method 1: sys module. Pros: Direct and comes with Python by default. Cons: Limited to the native Python float type. May not provide in-depth information for specialized types.
  • Method 2: numpy module. Pros: Extends float limit information to other data types. Cons: Requires NumPy installation and slightly heavier than sys module.
  • Method 3: decimal module. Pros: Provides precision and limits in the context of decimal arithmetic. Cons: More geared towards decimals, so may not be directly relevant for all float operations.
  • Method 4: mpmath module. Pros: Offers high-precision arithmetic insights. Cons: Requires installing a third-party package and might be overkill for simple applications.
  • Bonus Method 5: float’s __repr__. Pros: Quick and easy to use in a pinch. Cons: Offers minimal and somewhat cryptic information that may not be immediately useful for understanding precision or limits.