Modify 2D Array (Python)

Question

Hey guys so I have a 2D array that looks like this:

12381.000  63242.000     0.000     0.000     0.000     8.000     9.200     0.000     0.000     
12401.000  8884.000     0.000     0.000    96.000   128.000   114.400    61.600     0.000    
12606.000  74204.000    56.000    64.000    72.000    21.600    18.000     0.000     0.000     
12606.000  105492.000     0.000     0.000     0.000     0.000     0.000     0.000    45.600     
12606.000  112151.000     2.400     4.000     0.000     0.000     0.000     0.000     0.000     
12606.000  121896.000     0.000     0.000     0.000     0.000     0.000    60.800     0.000     

(Cut off couple of columns due to formatting)

So it indicates the employee ID, Department ID, followed by the 12 months worked by each employee and the hours they worked for each month. My 2D array is essentially a list of lists where each row is a list in its own. I am trying to convert each nonzero value to a one and maintain all the zeros. There are 857 rows and 14 columns. My code is as follows:

def convBin(A):
    """Nonzero values are converted into 1s and zero values are kept constant.
    """
    for i in range(len(A)):
        for j in range(len(A[i])):
            if A[i][j] > 0:
                A[i][j] == 1
            else:
                A[i][j] == 0
    return A

Can someone tell me what I am doing wrong?

Answer 1

You are doing equality evaluation , not assignment , inside your loop:

A[i][j] == 1

should be

A[i][j] = 1
      # ^ note only one equals sign

Also, there is no need to return A ; A is being modified in-place, so it is conventional to implicitly return None by removing the explicit return ... line.

You should bear in mind that:

• You don't actually want to do anything in the else case; and
• Iterating over range(len(...)) is not Pythonic - use eg enumerate .

Your function could therefore be simplified to:

def convBin(A):
    """Convert non-zero values in 2-D array A into 1s."""
    for row in A:
        for j, val in enumerate(row):
            if val:
                row[j] = 1