包含或不包含[：]之间的区别

Question

两个声明都产生相同的结果，但是我想知道幕后的区别是什么。

a = [1,2,3,4,5]
a[:] = a[0:3]
print(a)
a = [1,2,3,4,5]
a = a[0:3]
print(a)

Answer 1

这可以用另一个变量更好地解释。

假设a和b相同。当我们使用切片分配时，a和b都会更改，因为它们是相同的列表。无需将其分配给均值切片，就可以创建一个新的列表，称为a，该列表与b不再相关。

a = b = [0, 1, 2]
a[:] = a[0:2]
# a and b point to the same object and that got changed
print(a)  # gives [0, 1]
print(b)  # gives [0, 1]

a = b = [0, 1, 2]
a = a[0:2]
# a and b point to two different objects sharing no memory together
print(a)  # gives [0, 1]
print(b)  # gives [0, 1, 2]