hi: with script data = open('134-176_rectified_edited.pdb', 'r') outp = open('134-176_renumbered.pdb', 'w')
for L in data: if L[3] == 'M': L = L[:24] + "%4d" % (int(L[24-28])+133) + L[28:] outp.write(L) i wanted to modify lines of the type: ATOM 1 HH31 ACE 1 1.573 1.961 0.769 1.00 0.00 H to add 133 to column 25, getting 134 there, and so on for next lines 2 -> 135, 3 -> 136, etc. i must have heavily messed things because the file was not even read: $ python renumber.py 134-176_rectified.pdb Traceback (most recent call last): File "renumber.py", line 6, in <module> L = L[:24] + "%4d" % (int(L[24-28])+133) + L[28:] ValueError: invalid literal for int() with base 10: '' thanks for having an expert look chiendarret -- http://mail.python.org/mailman/listinfo/python-list