python conversion of two dimensional list of float to two dimensional array of float
Question: I am trying to read a column of float into a list for each of a set of CSV
files, then appending to a two dimensional list, later converting that to a 2D
array, but the array doesn't convert into a two dimensional array of float
(paraphrased below). Where am I going wrong?

    
    
    import numpy
    symbols = ['CVX', 'COP', 'MMM', 'BP', 'HMC', 'TM']
    AA_lst = []
    nSyms = len(symbols)
    shortest = 99999
    for sym in symbols
        fn = "PricesOf_" + sym + ".csv"
        col = getCSVcolumn( fn, "Close" )
        print( "type(col)="    + str(type(col)) )     # --> <class 'list'>
        print( "type(col[0])=" + str(type(col[0])) )  # --> <class 'float'>
        shortest = min(shortest,len(col))
        AA_lst.append(col)                            # appended as a row of AA_lst
    
    AA = numpy.array( AA_lst )
    print( "type=(AA)="     + str(type(AA)) )         # --> <class 'numpy.ndarray'>
    print( "type=(AA[0]="   + str(type(AA[0])) )      # --> <class 'list'>
    #print( "type=(AA[0,0]=" + str(type(AA[0,0])) )   # --> Error, too many indices
    
    # fix up dimensions (so rows are all the same length)
    AA = numpy.resize( AA, (nSyms, shortest) )
    print( "type=(AA)="     + str(type(AA)) )         # --> <class 'numpy.ndarray'>
    print( "type=(AA[0]="   + str(type(AA[0])) )      # --> <class 'numpy.ndarray'>
    print( "type=(AA[0,0]=" + str(type(AA[0,0])) )    # --> <class 'list'>
    
    # desire something of the form:  array([[1,2,3] [4,5,6] [7,8,9]])
    # i.e. expecting type(AA[0,0] to be <class 'float'>, not <class 'list'>
    


Answer:   1. Make sure the lists in `AA_lst` are of the same length.
  2. Consider using [pandas](http://pandas.pydata.org/).

