UnboundLocalError: local variable 'i' referenced before assignment when shallow copying a c3d file with no events

[jaraujo98]

When copying a c3d file with no events the variable i in this line is never defined, and the code crashes.

py-c3d/c3d/c3d.py

Line 490 in 090544a

write_count = min(i + 1, 18)

Is fixing this as easy as just returning an empty list, or is there more to it? If it's just returning an empty list, happy to open a PR for it.

[friggog]

Just adding something like

if not events:
   return

at the top of this function seems like it would work?

[MattiasFredriksson]

Not sure if returning immediately is the best option as it's not a 'protected' function and a user should be allowed to pass in an empty list to 'clear' the event block. Not sure what the best option is however since the loop is a bit odd as it allows an iterator to be passed in which doesn't have len(). Removing the line and refactoring the loop might be a better solution:

write_count = 0 # Initiate counter in-case events is an empty iterator
for time, label in events:
    if write_count == 18:
        # Don't raise Error, header events are rarely used.
        warnings.warn('Maximum of 18 events can be encoded in the header, skipping remaining events.')
        break

    event_timings[write_count] = time
    event_labels[write_count] = label
    label_bytes[write_count * 4:(write_count + 1) * 4] = label.encode('utf-8')
    write_count += 1

Extending the doc-string might be good idea as well to just to inform the caller that it accepts an empty list.

[MattiasFredriksson]

Updated the answer to adjust the behavior of the for loop.