Table of contents
shape() function in python
The shape function is a function in numpy.core.fromnumeric, and its function is to read the length of the matrix .
1. shape() input parameters
(1) When the parameter is a number, return empty
(2) The parameter is a one-dimensional matrix
(3) The parameter is a two-dimensional matrix
2. Determine the dimension of the array
- There are several square brackets for a few-dimensional array
shape（）中有3个数。
a = np.array([1,2]) #a.shape值(2,)，意思是一维数组，数组中有2个元素。
b = np.array([[1],[2]]) #b.shape值是(2,1)，意思是一个二维数组，每行有1个元素。
c = np.array([[1,2]]) #c.shape值是（1，2），意思是一个二维数组，每行有2个元素。
- Use shape[0] to read the length of the first dimension of the matrix, that is, the number of rows; use shape[1] to read the length of the second dimension of the matrix, that is, the number of columns.
import numpy as np
x = np.array([[1,2,5],[2,3,5],[3,4,5],[2,3,6]])
#输出数组的行和列数
print x.shape #结果： (4, 3)
#只输出行数
print x.shape[0] #结果： 4
#只输出列数
print x.shape[1] #结果： 3
3. The meaning of "?" in shape()
When debugging related programs, shape(?,2,3) may appear, which means that each array has 2 rows and 3 columns. The "?" in front of it represents the number of batches. If it is 1, there is 1 If it is 2, there are two, but I don't know how many there are when debugging, so it is displayed in the form of "?".