Why Does Python\'s `range()` Function Exclude the Upper Bound?

Why Range Functions Exclude the Upper Bound

In Python, the range(start, end) function generates a sequence of numbers starting from start and ending before end. This behavior can be confusing to some users who expect the range to include end.

The reason for this exclusion lies in the common usage of range(0, 10). When used with a start of 0, range returns [0, 1, 2, 3, 4, 5, 6, 7, 8, 9], which is the desired sequence with 10 elements. This matches the length of the sequence generated, ensuring that the number of iterations is correct in loops and other applications.

Additionally, excluding the upper bound allows for cleaner loop syntax. Consider the code snippet:

for i in range(len(li)):
    pass

If range included end, the above code would throw an error when i reached len(li) because it would attempt to access an element outside the list's bounds. Excluding the upper bound eliminates this potential error.

Programmers commonly prefer to use for loops with i ranging from 0 to len(li) - 1 rather than 1 to len(li). This is due to the prevalence of 0-based indexing in programming.

For users who prefer to include the upper bound, a custom function can be created:

def range1(start, end):
    return range(start, end + 1)

Using range1(1, 10) will produce the desired sequence of [1, 2, 3, 4, 5, 6, 7, 8, 9, 10].

The above is the detailed content of Why Does Python\'s `range()` Function Exclude the Upper Bound?. For more information, please follow other related articles on the PHP Chinese website!