MatApp.. a program i just made

# Ver. 1.3
def return_int(y):
    while True:
        v = raw_input("%s" % y)
        try:
            v = int(v)
        except ValueError:
            print "Should be an integer number"
        else:
            return v

def return_float(y):
    while True:
        v = raw_input("%s" % y)
        try:
            v = float(v)
        except ValueError:
            print "Should be a number"
        else:
            return v

def form_mat():
    matrix = []
    x = []
    print "Matrix RxC"
    print "Rows no^|^Columns no"
    i = 1
    while True:
        y = raw_input("Please enter raw no. (%i): " % (i))
        if (y.strip()).lower() == 'end':
            break
        if y == '':
            continue
        x = y.split()
        j = 0
        while j < len(x):
            try:
                x[j] = float(x[j])
            except ValueError:
                print "Value Error!!"
                x = []
                i -= 1
                break
            else:
                j += 1
        matrix += [x]
        x = []
        i += 1
    for z, v in enumerate(matrix):
        if len(v) == 0:
            del matrix[z]
    while True:
        l = [len(i) for i in matrix]
        a, b = max(l), min(l)
        if a != b:
            d = a - b
            print """
The number of columns aren't identical..
You have to enter %i element(s) in row %i
""" % (d, l.index(b)+1)
            while True:
                x = raw_input("Please enter: ")
                y = x.split()
                if len(y) < d:
                    print "Less than needed!!"
                    continue
                elif len(y) > d:
                    print "More than needed!!"
                    continue
                else:
                    try:
                        for i, v in enumerate(y):
                            y[i] = float(v)
                    except ValueError:
                        print "Value Error!!"
                    else:
                        matrix[l.index(b)] += y
                        break
        else:
            break
    return matrix

def add_row(mat):
    temp = []
    i = 0
    while i < len(mat[0]):
        element = raw_input("Please enter element(%i)(%i): " % (len(mat)+1, i+1))
        try:
            element = float(element)
        except ValueError:
            print "Not a number!"
        else:
            temp += [element]
            i += 1
    mat += [temp]
    return mat

def add_column(mat):
    temp = []
    i = 0
    x = len(mat[0])+1
    while i < len(mat):
        element = raw_input("Please enter element(%i)(%i): " % (i+1, x))
        try:
            element = float(element)
        except ValueError:
            print "Not a number!"
        else:
            mat[i].append(element)
            i += 1
    return mat

def row_times_column(m1, row, m2, column):
    temp = 0
    for i in range(len(m1[row])):
        temp += m1[row][i]*m2[i][column]
    return temp

def matrix_mult(m1, m2):
   result = []
   temp = []
   for i in range(len(m2[0])):
      for j in range(len(m1)): # The reason for taking m2[0] and m1 is that if there were 2 matrices one of 2x3 and the other of 3x2 so the resulting matrix will be of 2x2
         temp += [row_times_column(m1, i, m2, j)]
      result += [temp]
      temp = []
   return result

def scalar_mult(n, m):
    result = []
    temp = []
    for i in range(len(m)):
        for j, v in enumerate(m[i]):
            temp += [v*n]
        result += [temp]
        temp = []
    return result

def add_mat(a, b):
    # The first 3 lines are aimed to check that both matrices have the same number of rows and columns
    if len(a) == len(b):
        for i in range(len(a)):
            if len(a[i]) != len(b[i]):
                print "The matrices don't have the same number of columns.."
                break
            else: # The addition starts from here..
                result = []
                temp = []
                for i in range(len(a)):
                    for j in range(len(a[0])):
                        temp += [a[i][j] + b[i][j]]
                    result += [temp]
                    temp = []
                return result
    else:
        print "Matrices don't have the same number of rows.."

print "Please type 'help' for help"
print "type 'new' for assigning a new matrix"
mat_no = 0
mat1 = []
mat2 = []
while True:
    user_order = raw_input(">>> ")
    if (user_order.strip()).lower() == 'new':
        if mat_no == 0:
            mat1 = form_mat()
            mat_no += 1
            for i in mat1:
                print i
        elif mat_no == 1:
            mat2 = form_mat()
            mat_no += 1
            for i in mat2:
                print i
        else:
            print "You already assigned two matrices (maximum number of them)"
            ask = raw_input("If you want to replace one press 'n', else just press enter")
            if ask == 'n' or ask == 'N':
                choice = return_int('Please choose number 1 or number 2: ')
                if choice == 1:
                    mat1 = form_mat()
                elif choice == 2:
                    mat2 = form_mat()
                else:
                    print "Wrong choice"
            else:
                pass
            
    elif (user_order.strip()).lower() == 'add_mat':
        print add_mat(mat1, mat2)
    
    elif (user_order.strip()).lower() == 'add_column':
        if len(mat2) == 0:
            mat1 = add_column(mat1)
        elif len(mat1) == 0:
            print "You didn't assign any matrices yet!"
        else:
            choice = return_int('Please choose number 1 or number 2: ')
            if choice == 1:
                mat1 = add_column(mat1)
            elif choice == 2:
                mat2 = add_column(mat2)
            else:
                print "Wrong choice"
                
    elif (user_order.strip()).lower() == 'add_row':
        if len(mat2) == 0:
            mat1 = add_row(mat1)
        elif len(mat1) == 0:
            print "You didn't assign any matrices yet!"
        else:
            choice = return_int('Please choose number 1 or number 2: ')
            if choice == 1:
                mat1 = add_row(mat1)
            elif choice == 2:
                mat2 = add_row(mat2)
            else:
                print "Wrong choice"

    elif (user_order.strip()).lower() == 'scalar':
        if len(mat2) == 0:
            n = return_float('please enter the number: ')
            print scalar_mult(n, mat1)
        elif len(mat1) == 0:
            print "No matrices are available"
        else:
            choice = return_int('Please choose number 1 or number 2: ')
            if choice == 1:
                n = return_float('please enter the number: ')
                print scalar_mult(n, mat1)
            elif choice == 2:
                n = return_float('please enter the number: ')
                print scalar_mult(n, mat2)
            else:
                print "Wrong choice"
                
    elif (user_order.strip()).lower() == 'mult_mat':
        print matrix_mult(mat1, mat2)

    elif (user_order.strip()).lower() == 'mult_rc':
        row = return_int('row number: ')
        column = return_int('column number: ')
        print row_times_column(mat1, row, mat2, column)

    elif (user_order.strip()).lower() == 'exit':
        exit()

    elif (user_order.strip()).lower() == 'help':
        print """
The syntax of available functions are listed below with description..
Note that case is NOT sensitive;
for example, you can enter the command (new) like this
>>> NeW

Also, leaving whitespaces before or after the command have no effect;
for example, you can write the command (add_mat) like this
>>>         add_mat

Note: Adding or Removing a letter from the command will afect the command
i.e. your command won't work and a message appears telling you "Not available choice."

(new)
with this, you can assign a new matrix
there are only two places available for the matrices i.e. you can only assign two matrices
The matrix is passed to the program row by row each element is separated by just ONE space
for example:
Please enter raw no. (1): 1 2 3 4
Please enter raw no. (2): 5 6 7 8

(add_mat)
with this, you can add two matrices
both of them should be pre-assigned
if there wasn't the second an error may occur which leads to force the program to be closed

(add_row)
with this, you can add a new row to a pre-assigned matrix

(add_column)
with this you can add a new column to a pre-assigned matrix

(scalar)
with this, you can multiply a number with a matrix

(mult_mat)
with this, you can multiply both matrices
note: be sure that you have already entered two matrices, otherwise an error may occur leading the program to be closed

(mult_rc)
with this, you can have the result of multiplication of a specific row and scpecific column
You are the one who is going to specify the row and the column

(show)
with this, you can see the matrices you assigned
if the matrix was empty, it will give you something like this:
Matrix #1:
[]

(exit)
To close the program
"""
    elif (user_order.strip()).lower() == "show":
        print "Matrix #1:"
        print mat1
        print "Matrix #2:"
        print mat2
    else:
        print "Not available choice."

try:
    # try_block
finally:
    #finally_block