问题:

I'm creating very simple charts with matplotlib / pylab Python module. The letter "y" that labels the Y axis is on its side. You would expect this if the label was longer, such as a word, so as not to extend the outside of the graph to the left too much. But for a one letter label, this doesn't make sense, the label should be upright. My searches have come up blank. How can I print the "y" horizontally?

回答1:

It is very simple. After plotting the label, you can simply change the rotation:

from matplotlib import pyplot as plt
plt.ion()
plt.plot([1,2,3])
h = plt.ylabel('y')
h.set_rotation(0)
plt.draw()

Alternatively, you can pass the rotation as an argument, i.e

plt.ylabel('y',rotation=0)

回答2:

Expanding on the accepted answer, when we work with a particular axes object ax:

ax.set_ylabel('abc', rotation=0, fontsize=20, labelpad=20)

Note that often the labelpad will need to be adjusted manually too — otherwise the "abc" will intrude onto the plot.

From brief experiments I'm guessing that labelpad is the offset between the bounding box of the tick labels and the y-label's centre. (So, not quite the padding the name implies — it would have been more intuitive if this was the gap to the label's bounding box instead.)