Is there a way to use ax.margins to adjust the axes limits, after the axes limits have already been adjusted using ax.set_ylim? It appears that ax.margins has effect only if ax.set_ylim has not been used.

This notebook
http://nbviewer.jupyter.org/github/qap/offline_radiation_notebooks/blob/lblnew/longwave/lblnew_20160916/study__g1_threshold/n2o/band07_wn_1215_1380/P_50_T_250/4.e-21/matplotlib_axmargins.ipynb

describes a situation in which this need may arise.

Note: the y-axis is just an example, the same also applies to the x-axis (ax.set_xlim).