Why Does Python Use an Exclusive Upper-Bound in Slices and Ranges?

Exploring Python's Exclusive Upper-Bound for Slices and Ranges

In Python, the slice and range functions operate with an exclusive upper-bound. This means that when specifying a range or slice, the stop value is not included in the result. Why is this the case?

Maintaining Consistency with C for Loops

One possible reason for using an exclusive upper-bound is to align with the C for loop idiom. In C, the for loop syntax is:

<code class="C">for (i = start ; i < stop; i++) {
    // ...
}</code>

By using an exclusive upper-bound in Python, the for loop syntax

<code class="Python">for i in range(start, stop):
    # ...</code>

superficially resembles the C idiom, making it easier for programmers familiar with both languages.

Useful Invariants and Properties

However, the documentation also highlights several useful invariants and properties of exclusive upper-bound slicing and ranging:

• s[:i] s[i:] equals s.
• The length of a slice is the difference of the indices, if both are within bounds (e.g., word[1:3] has a length of 2).

These properties enable concise and efficient operations, such as:

• Extracting the first two characters: word[:2]
• Extracting everything except the first two characters: word[2:]
• Calculating the length of a slice: len(word[1:3])

Consistency Across Range and Slice Functions

Additionally, maintaining consistency between the range and slice functions allows for seamless interoperability. Using the same exclusive upper-bound rule ensures that slices and ranges behave consistently, simplifying code readability and maintainability.

The above is the detailed content of Why Does Python Use an Exclusive Upper-Bound in Slices and Ranges?. For more information, please follow other related articles on the PHP Chinese website!