matplotlib colorbar not working (due to garbage collection?)
garbage-collection, ipython, matplotlib, python
Solution
It is because you first example, you are using `ax.polormesh`, not `pyplot.polotmesh` (namespace imported by `pylab`), when you call `colorbar()` (actually `plt.colorbar()`), it lost track of which mappable and which ax it should make colorbar to.
Therefore adding these lines will make it work:
import matplotlib.pyplot as plt
fct()
ax=plt.gca() #get the current axes
PCM=ax.get_children()[2] #get the mappable, the 1st and the 2nd are the x and y axes
plt.colorbar(PCM, ax=ax)
Now you mentioned that your actual plot is a much more complex one. You want to make sure it is the `ax.get_children()[2]` or you can pick the it by look for a `matplotlib.collections.QuadMesh` instance.
Problem
I have a plotting function similar to this one ``` def fct(): f=figure() ax=f.add_subplot(111) x,y=mgrid[0:5,0:5] z=sin(x**2+y**2) ax.pcolormesh(x,y,z) ``` When I define the function above in `ipython` (using the `--pylab` option), and then call ``` fct() colorbar() ``` I get an error "RuntimeError: No mappable was found to use for colorbar creation.". ``` def fct(): f=figure() x,y=mgrid[0:5,0:5] z=sin(x**2+y**2) pcolormesh(x,y,z) ``` Then it works. I guess this has to do with garbage collection - how can I prevent this problem in the first example?