Range of float in python
In Python, the range of float values depends on the implementation and the platform. The Python language specification only requires that floating-point numbers support at least 1e-308 to 1e+308 with a precision of at least 53 bits.
In practice, most modern Python implementations use the IEEE 754 floating-point standard, which provides a range of approximately 1.7e-308 to 1.7e+308 with a precision of 53 bits. This range is the same on all platforms and is supported by the float built-in type.
However, it is important to note that floating-point arithmetic is subject to rounding errors and other sources of imprecision, especially when performing operations on very large or very small numbers. It can lead to unexpected behavior and bugs in some cases.
To avoid these issues, it is often recommended to use decimal or fixed-point arithmetic when working with monetary values or other applications that require high precision. The decimal module in Python provides support for fixed-point arithmetic with configurable precision and is a good alternative to floating-point arithmetic for these applications.
The IEEE 754 standard defines the range and precision of floating-point numbers used by most modern programming languages, including Python. The standard defines two basic formats for floating-point numbers:
It uses 32 bits and provides approximately 7 decimal digits of precision.
It uses 64 bits and provides approximately 16 decimal digits of precision.
Python uses double-precision floating-point numbers by default, which means that the range of float values is approximately 1.7e-308 to 1.7e+308 with a precision of 53 bits. This range is determined by the maximum and minimum exponents that can be represented using 11 bits, combined with the maximum and minimum significands (i.e., the fraction part of the number) that can be represented using 52 bits.
The actual precision of floating-point arithmetic can be affected by many factors, including the way that numbers are stored in memory, the order of operations, and the choice of rounding mode. It can lead to subtle rounding errors and other sources of imprecision in some cases.
To avoid these issues, it is often recommended to use alternative approaches when working with very large or very small numbers, or when high precision is required. For example:
One important aspect to note is that when performing arithmetic operations on floating-point numbers in Python, you may encounter some unexpected behavior due to the way that floating-point arithmetic works.
Some arithmetic operations may result in very small or very large numbers that cannot be represented precisely using floating-point arithmetic. In these cases, the result may be rounded or truncated, leading to unexpected behavior or inaccuracies in your calculations.
Floating-point arithmetic is not associative, which means that the order in which you perform operations can affect the result. For example, (a + b) + c may not be equal to a + (b + c) due to rounding errors and other sources of imprecision.
Floating-point arithmetic is also not distributive, which means that (a + b) * c may not be equal to a * c + b * c due to rounding errors and other sources of imprecision. To minimize the impact of these issues, it's often recommended to use the math module or other numerical libraries that provide functions for performing arithmetic operations on floating-point numbers in a more precise and reliable manner. It is also a good practice to avoid comparing floating-point numbers for equality, and instead to use a tolerance threshold or other methods for comparing the magnitude of the difference between two values.
Let's take an example to show how floating-point arithmetic can lead to unexpected behavior in python:
In this example, we are performing two different calculations using the same values of a, b, and c. In the first calculation, we add a and b first, and then add the result to c. In the second calculation, we add b and c first, and then add the result to a.
We might expect the two calculations to produce the same result, since they use the same values of a, b, and c. However, due to the limitations of floating-point arithmetic, the two calculations produce slightly different results.
The first calculation produces a result of 0.6000000000000001, while the second calculation produces a result of 0.6. It is because the intermediate results of the first calculation are slightly different from the intermediate results of the second calculation, due to rounding errors and other sources of imprecision.
To avoid these issues, it's often recommended to use the decimal module or other methods for performing arithmetic operations on floating-point numbers in a more precise and reliable manner.
In this example, we use the decimal module to perform the same calculations using fixed-point arithmetic with a precision of 1 decimal place. It allows us to avoid the rounding errors and other sources of imprecision that can affect floating-point arithmetic. As a result, both calculations produce the same result of 0.6.
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