Write a function that reads stock share price at of N industries  for M days as a two dimensional array and prints the diagonal price of the stock .

Sure, here is a Python function that does that:

def print_diagonal_prices(stock_prices):
    # Get the length of the 2D array
    n = len(stock_prices)
    
    # Loop through the 2D array
    for i in range(n):
        # Print the diagonal element
        print(stock_prices[i][i])

This function takes a 2D list stock_prices as input, where each row represents an industry and each column represents a day. It then prints the diagonal elements of this 2D list, which represent the stock prices of each industry on a certain day.

Here's how you can use this function:

# Define the 2D list of stock prices
stock_prices = [[10, 20, 30], [40, 50, 60], [70, 80, 90]]

# Call the function
print_diagonal_prices(stock_prices)

This will print:

10
50
90

This means that the stock price of the first industry on the first day was 10, the stock price of the second industry on the second day was 50, and the stock price of the third industry on the third day was 90.