The smallest valid alpha value in matplotlib?
There's no lower limit; the lines just appear to be invisible for very small alpha values.
If you draw one line with alpha=0.01 the difference in color is too small for your screen / eyes to discern. If you draw 100 lines with a=0.01 on top of each other, you will see them.
As for your problem, you can just add a small number to the alpha value of each draw call so that lines that would otherwise have alpha < 0.1 still appear.
Some of my plots have several million lines. I dynamically adjust the alpha value, by the number of lines, so that the outliers more or less disappear, while the most prominent features appear clear. But for some alpha's, the lines just disappear.
What is the smallest valid alpha value for line plots in in matplotlib? And why is there a lower limit?