import numpy as np
from tempfile import NamedTemporaryFile as Tmp

def load_csv_file(fname, *args, **kargs):
    f = open(fname)
    data = np.genfromtxt(f, delimiter=",", comments="#",
                         *args, **kargs)
    f.close() # don't leak file handles
    return data

def write_csv_file(fname, rows, header=None, width=None):
    if fname is None:
        f = Tmp()
    else:
        f = open(fname, 'w')
    if width:
        fmt = "%%%ds" % width
    else:
        fmt = "%s"

    if header:
        f.write('#')
        f.write(", ".join([fmt % str(x) for x in header]))
        f.write('\n')
    for row in rows:
        f.write(' ')
        f.write(", ".join([fmt % str(x) for x in row]))
        f.write('\n')
    if fname is None:
        # keep it open
        f.flush()
        return f
    else:
        f.close()

def select(keep, rows):
    ok_rows = np.zeros(len(rows), dtype=bool)
    for i, row in enumerate(rows):
        ok_rows[i] = keep(row)
    return rows[ok_rows]