Multiple for loops in Sudoku solver
A for statement can have an else clause which suits your needs perfectly and allows you to eliminate the variable hidden. I would also prefer a simple if instead of the if pass elif construct:

for num in cell.getAvailNum():              # For each available number for the cell we are looking at
    for tempCell in colCells:               # For each cell in the list of cells
        if tempCell != cell and num in tempCell.getAvailNum(): # If one of the available num is the same
            break
    else: 
        cell.setAvailNum(num)               # If hidden is still true, set available num to num
        break