为什么它跳过数组输入的第一行

Question

Input Format

The first line contains the space separated values of N and M. The next lines contain the space-separated elements of columns.

input
2 2
1 2
3 4

the code

import numpy


my_array = numpy.array([input().split() for _ in range(int(input().split()[0]))],int)

print(my_array.T,my_array.flatten(),sep = "\n")

while taking input for the array how the code skips the first line "2 2" containing number of rows and number of columns, i just want an understanding of how it starts taking input from the second line

output
[[1 3]
 [2 4]]
[1 2 3 4]

Answer 1

This code uses list comprehension, in which the call of the latter input() reads the first line, so that it takes input from the second line.

This code is equivalent to:

import numpy as np

# Read the first line.
num_rows = int(input().split()[0])

# Deal with data.
rows = []
for __ in range(num_rows):
    rows.append(input().split())
my_array = np.array(rows, int)

print(my_array.T, my_array.flatten(), sep='\n')

Answer 2

First, the for _ in range(int(input().split()[0])) gets executed and the first line (in your sample input, 2 2 ) is read from the input. Then for the range obtained from the executed range(int(input().split()[0])) the next lines would be read. In your sample input, first the for _ in range(int(input().split()[0])) will be executed, which is actually for _ in range(2)) and then the 2 next lines will be read with input().split() .