Is There Any Difference Between math.inf and float('Inf') in Python?

Other than the fact that math.inf and -math.inf were introduced in Python 3.5, there are no differences between them, and float('inf') and float('-inf'). They both follow the IEEE 754 floating-point standard and are equivalent representations of positive and negative infinity, respectively. Therefore, they can be used interchangeably. In fact, when you check the type of these values, you'll find that they are all of the same type:

import math

print(type(math.inf)) # <class 'float'>
print(type(float('inf'))) # <class 'float'>

print(type(-math.inf)) # <class 'float'>
print(type(float('-inf'))) # <class 'float'>

These representations can be used interchangeably in mathematical calculations, comparisons, and other operations. For instance, consider the following, where the math.isinf() function can be seen to be compatible with both math.inf and float('inf') (and their negative counterparts):

import math

print(math.isinf(math.inf)) # True
print(math.isinf(-math.inf)) # True

print(math.isinf(float('inf'))) # True
print(math.isinf(float('-inf'))) # True

print(math.isinf(42)) # False

Similarly, you can directly compare the values against either math.inf or float('inf') (and their negative equivalents):

import math

print(math.inf == float('inf')) # True
print(-math.inf == -float('inf')) # True

In the examples above, you can see that the values are equivalent to each other. The decision to choose one over the other typically depends on personal preference or the specific coding context. However, the math.inf form is often preferred for semantics, readability and clarity.