你的程序有很多硬编码的片段下标，你不能直接看到，然后你想要清理代码。
[En]
Your program has a lot of hard-coded slice subscript that you can’t see directly, and then you want to clean up the code.
假设您有一段从记录字符串的固定位置提取特定数据字段的代码：
[En]
Suppose you have a piece of code to extract a specific data field from a fixed position in a record string:
record = '....................100 .......513.25 ..........'
cost = int(record[20:23]) * float(record[31:37])
事实上，命名切片可用于避免大量难以理解的硬编码下标，并使代码更具可读性。
[En]
In fact, named slices can be used to avoid a large number of hard-coded subscripts that are incomprehensible and make the code more readable.
SHARES = slice(20, 23)
PRICE = slice(31, 37)
cost = int(record[SHARES]) * float(record[PRICE])
一般来说，如果代码中有大量的硬编码下标，代码的可读性和可维护性会大大降低。命名切片是更清楚地表达代码想要做什么的好方法。
[En]
Generally speaking, if there are a large number of hard-coded subscripts in the code, the readability and maintainability of the code will be greatly reduced. Naming slices is a good way to express what your code wants to do more clearly.
内置的函数 slice()函数创建了一个切片对象，可以被使用在任何切片允许使用的地方。比如：
items = [0, 1, 2, 3, 4, 5, 6]
a = slice(2, 4)
items[2:4] # [2, 3]
items[a] # [2, 3]
items[a] = [10, 11] # items = [0, 1, 10, 11, 4, 5, 6]
del items[a] # item = [0, 1, 4, 5, 6]
如果你有一个切片对象 a，你可以分别调用它的 a.start， a.stop， a.step属性来获取更多的信息。比如：
a = slice(5, 50, 2)
a.start # 5
a.stop # 50
a.step # 2
另外，你还能通过调用切片的 indices(size)方法将它映射到一个确定大小的序列上，这个方法返回一个三元组(start, stop, step)，所有值都会被合适的缩小以满足边界限制，从而避免出现 IndexError异常。比如：
s = 'HelloWorld'
a = slice(5, 10, 2)
d = a.indices(len(s))
"""
d = (5, 10, 2)
"""
for i in range(*d):
print(s[i])
"""输出结果
W
r
d
"""
Original: https://www.cnblogs.com/L999C/p/15731595.html
Author: Abu11
Title: 1.11 命名切片
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