def greeting():
    print 'This program tries to open a file with the name provided by the user,\n',
    print 'and read all the data into a two-dimensional array/list'
    print 'The data must consist of integer numbers, separated by spaces.',

def processData(data):
    rows = len(data) # number of rows is the number of elements in the list
    # number of columns is the number of elements is each string of the list
    # we will get later

    print 'number of lines is %d'%rows
    
    A=list()

    cols=0
    for r in range(rows):
        line=data[r].split() # split by white space, store is a list

        if r == 0: # getting the number of elements in each string of the list
            cols=len(line)
            print 'number of elements in each line is %d'%cols

        if len(line) != cols:
            print 'Warning: line %d:'%(cols+1)

            raise ValueError('number of elements in this line is different from the lines above')

        # use list comprehension to convert each element to integer
        line_int=[int(elem) for elem in line]
            
        # appent the list of integers to list A as a next element of list A
        A.append(line_int)

    return A

def display(A):

    cols=len(A[0])
    for i in range(len(A)):
        for j in range(cols):
            print A[i][j],
        print

def main():

    greeting()

    while True:

        fname=raw_input('Please, input the name of the data file:')
        
        try:
            f=open(fname)
            break
        except ValueError:
            print 'cannot open file %s'%fname
            

    print 'File %s opened successfully!'%fname

    
    # read all the data from the given data file
    # store it in a list, the result is a list of strings
    data = f.readlines()

    # form a two-dimensional array
    A=processData(data)

    # display the information
    display(A)

main()