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+--- Thread: Print 2D Array (/thread-15433.html)
Print 2D Array - dragu_stelian - Jan-17-2019
Hello!
I am new in Python and I have a question.
In the next code I want to print a 2D array in "C++ style"
tab = [[]]
rows = int(input("Enter size of the rows: "))
cols = int(input("Enter size of the cols: "))
for i in range(0, rows):
for j in range(0, cols):
arr = int(input("tab[{}][{}] = ".format(i,j)))
tab.append(arr)
print()
for i in range(len(tab)):
print(tab[i], end = " ")
print()For a tab[2][3] the below code will print:Enter size of the rows: 2
Enter size of the cols: 3
tab[0][0] = 11
tab[0][1] = 12
tab[0][2] = 13
tab[1][0] = 21
tab[1][1] = 22
tab[1][2] = 23
[] 11 12 13 21 22 23
Why square brackets at the beginning ?
There are many ways to print the 2D array in Python ?
RE: Print 2D Array - buran - Jan-17-2019
To answer your question - on line 1 you initialize the tab list with empty list, i.e. your tab list already has 1 element before you input rest values and append them to tab list.
make line 1
tab = []However I don't think the result is what you expect - tab is a list, not list of lists if that is what you expect
RE: Print 2D Array - perfringo - Jan-17-2019
What datastructure you want to build?
I assume that 2D array is list of lists (matrix). If so, you can create in several ways. Some examples:
>>> matrix = [] # create empty list named matrix >>> for i in range(3): ... matrix.append([]) # append empty list to end of matrix ... for j in range(4): ... matrix[-1].append(0) # append zeros to last list of matrix ... >>> print(matrix) [[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]] # matrix with three rows and four columnsIt can be done with list comprehension with one-liner:
>>> [[0 for i in range(4)] for j in range(3)] [[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]]Matrix with consecutive numbers with asking from user number of rows and columns:
rows = int(input('Number of rows: '))
cols = int(input('Number of columns: '))
mtx = [[i + cols * j for i in range(1, cols + 1)] for j in range(rows)]
print(mtx)In case of three rows and four columns this will print [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]Sometime there is need for creating matrices with random numbers in it. In these cases utility functions like below can be handy:
def matrix_with_double_digits(rows, cols):
return [[random.choice(range(10,100)) for i in range(cols)] for j in range(rows)]This will generate matrix with specified number of rows and columns populated with random two-digit numbers.
RE: Print 2D Array - aakashjha001 - Jan-27-2019
# this is one approach to create a 2D list in python.
#There are multiple ways of creating.
n = int(input())
a = []
for i in range(n):
row = input().split()
for i in range(len(row)):
row[i] = int(row[i])
a.append(row)
print(a)