Animation problem of Virgil Stokes.
Since I began the answer sequence, here's a little more. If this
overlaps other answers, I apologize.
About the third parameter
"/frames/ can be a generator, an iterable, or a number of frames."
This makes very little sense to me --- what does "or a number of
frames" mean?
The name "data_gen" could suggest its meaning (after having read the
doc).
I am not sure what you are referencing as "the doc"; but I did read
the documentation several times and English is my native language.
I am not trying to accuse you of anything, I simply underline that if
the documentation - as cited - mentions the word *generator*, and the
program contains the argument *data_gen*, which is OBVIOUSLY a generator
which *yields* some data, then this might have give you some clues
concerning its meaning.
Note please that the keyword parameters are specified extra.
I am aware of this. Perhaps, I am a Python dummy --- when I see
something like value = None in a Python API argument, I interpret this
as a keyword argument and not a generator.
1. Generators might be or not function arguments, keyword or not; this
is not an issue here. Generators are entities which produce iterators.
Here you have: *def data_gen(): while True: yield np.random.rand(10)* ,
and this is all.
2. When you see "frames=None", etc., this doesn't absolutely mean that
it is a kw parameter, just a positional parameter with a default value.
Brendan Barnwell commented this already.
If you look at the definition of the FuncAnimation class, which is
readable, in the file ... matplotlib/animation.py, you will see
*def __init__(self, fig, func, frames=None, init_func=None, fargs=None,
save_count=None, **kwargs):**
** ...*
which explicitly confirms this.
I think that you got the answers you demanded. The FuncAnimation
callback *requires* one argument, even if you don't use it. It may be
the frame number (or index if you wish), or explicit, specific data,
such as in your first example.
If, as in your second example, the parameter passed is the frame index,
and you want to see how you can use it, test this:
*x=np.linspace(0,20,300)***
* def update(i):*
**
**
* data=(np.sin(x+i/3)+1)/2*
**
* line.set_ydata(data)*
**
***
***
*ani = animation.FuncAnimation(fig, update, interval=40)*
You should see a moving sinusoid.
Please, in such cases test your programs by adding some simple
tracing contraptions, say, print(data) inside update.
I did this and more before posting my email. I would not have posted
this unless I thought it was necessary. And I thought one purpose of
this user group was to help people --- even if they ask a question
which may be annoying or "stupid" in some subscribers opinion. I try
to remember what a very wise teacher once said --- "there is no such
thing as a stupid question".
I don't understand your reaction. I teach computer science for many
years, and several times per week I suggest to my students to do this,
to trace their programs. I trace mine. Nobody feels offended. You said:
data is undefined. But it WAS DEFINED, you agree? So, printing its value
was the most natural suggestion. You would immediately see that it had
been generated by data_gen.
Also, I recommend that you look upon the sources of Matplotlib from time
to time. I do it regularly, it is nicely commented, and complements very
well the documentation.
Jerzy Karczmarczuk
PS. Some blizzard around positional/keyword parameters in Python is
quite persistent. "Dive into Python" of Mark Pilgrim covers this, and
offers some useful references.
See also this : https://www.python.org/dev/peps/pep-3102/
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