open file in “w” mode: IOError: [Errno 2] No such file or directory [duplicate]

You’ll see this error if the directory containing the file you’re trying to open does not exist, even when trying to open the file in w mode.

Since you’re opening the file with a relative path, it’s possible that you’re confused about exactly what that directory is. Try putting a quick print to check:

import os

curpath = os.path.abspath(os.curdir)
packet_file = "%s/%s/%s/%s.mol2" % ("dir", "dir2", "dir3", "some_file")
print "Current path is: %s" % (curpath)
print "Trying to open: %s" % (os.path.join(curpath, packet_file))

packetFile = open(packet_file, "w")