matplotlib animation FuncAnimation frames argument

Question

I'm using matplotlib animation by calling:

plot = animation.FuncAnimation(fig, update, frames=data_gen(a), init_func=init, interval=10, blit=True)

Here, "a" is an initial value for the data_gen function which looks like this:

data_gen(x)
    old_x = x
    while True:
        new_x = func(old_x)
        old_x = new_x
        yield new_x

The intention for this code is for data_gen to produce a new value for new_x each time the animated plot is updated.

BUT... this happens instead:

animation.py throws an error in the init() method of the FuncAnimation class.

The problem happens in this code:

elif iterable(frames):
    self._iter_gen = lambda: iter(frames)
    self.save_count = len(frames)

The error is "TypeError: object of type 'generator' has no len()"

It looks like data_gen is iterable but it has no len().

Here is more of the code for the init() method in the FuncAnimation class:

    # Set up a function that creates a new iterable when needed. If nothing
    # is passed in for frames, just use itertools.count, which will just
    # keep counting from 0. A callable passed in for frames is assumed to
    # be a generator. An iterable will be used as is, and anything else
    # will be treated as a number of frames.
    if frames is None:
        self._iter_gen = itertools.count
    elif isinstance(frames, collections.Callable):
        self._iter_gen = frames
    elif iterable(frames):
        self._iter_gen = lambda: iter(frames)
        self.save_count = len(frames)
    else:
        self._iter_gen = lambda: iter(list(range(frames)))
        self.save_count = frames

I'm not sure why my data_gen is not a collections.Callable. If it were, then len(frames) would never happen.

Any suggestions for what I should do about this would be appreciated!

matplotlib animation FuncAnimation frames argument

1 Answers