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matplotlib.axes.Axes.get_ylim
Axes.get_ylim()- 
    
Get the y-axis range
Returns: ylimits : tuple
Returns the current y-axis limits as the tuple (
bottom,top).Notes
The y-axis may be inverted, in which case the
bottomvalue will be greater than thetopvalue. 
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 http://matplotlib.org/2.0.2/api/_as_gen/matplotlib.axes.Axes.get_ylim.html