Analysis of specific problems in Python array practice

Python array has a lot of knowledge to learn in detail. Next we will learn more about the Python array. Hope to help you. The Python array does not have an array data structure, but the list is similar to an array, for example:

A = [, 2] Then a [0] = 0, a [1] = 1, a [[2] = 2, But this raises a problem, that is, if array a is to be defined as 0 to 999, it may be implemented through a = range (0, 1000. Or omitted as a = range (1000 ). if you want to define a with a length of 1000 and the initial value is all 0, a = [0 for x in range (0, 1000)] is the definition of a two-dimensional array:

Directly define a = [[], []. Here we define a two-dimensional array of 2*2 with an initial value of 0.

Indirectly define a = [[0 for x in range (10)] for y in range (10)]. Here we define a two-dimensional array with the initial value of 10*10 as 0.

Later, I found a simpler method to define two-dimensional arrays on the Internet:

B = [[0] * 10] * 10, which defines a two-dimensional array with the initial value of 10*10 as 0.

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Compare with a = [[0 for x in range (10)] for y in range (10)]: print a = B returns True.

However, after B's definition method is used to replace a, the previous programs that can run normally also failed. After careful analysis, the differences are obtained:

When a [0] [0] = 1, only a [0] [0] is 1, and all others are 0.

When B [0] [0] = 1, a [0] [0], a [1] [0], and only a [9, 0] is 1.

Therefore, the 10 small one-dimensional data in the large array is all referenced in the same way, that is, pointing to the same address.

Therefore, B = [[0] * 10] * 10 does not conform to the two-dimensional array in our general sense.

At the same time, the definition of c = [0] * 10 has the same effect as that of c = [0 for x in range (10, it is estimated that the Python array c is defined by multiplying the value type, while the previous B is multiplied by the type, because the one-dimensional array is a reference to borrow the value type and reference type in C, ).