Plot() in Pandas with two y-axes: Where is the second line stored?

I am using the integrated plot() function in pandas to generate a graph with two y-axes. This works well and the legend even points to the (right) y-axis for the second data set. But imho the legend's position is bad.

However, when I update the legend position I get two legends the correct one ('A', 'B (right)') at an inconvenient location, and a wrong one ('A' only) at the chosen location.

So now I want to generate a legend on my own and was looking for the second <matplotlib.lines.Line2D>, but it is not contained in the ax environment.

import pandas as pd
df = pd.DataFrame({"A":[1,2,3],"B":[1/4,1/5,1/6]})
ax = df.plot(secondary_y=['B'])
len(ax.lines)
>>> 1

My ultimate objective is to be able to move the correct legend around, but I am confident I could manually place a legend, if only I had access to the second line container.

If I had, I was going to suppress the original legend by invoking df.plot(...,legend=None) and do something like plt.legend([ax.lines[0],ax.lines[1]],['A','B (right)'],loc='center left',bbox_to_anchor=(1.2, 0.5)). But ax only stores the first line "A", where is the second?

Also ax.get_legend_handles_labels() only contains ([<matplotlib.lines.Line2D at 0x2630e2193c8>], ['A']).

You create two axes. Each contains a line. So you need to loop over the axes and take the line(s) from each of them.

import numpy as np
import pandas as pd

df = pd.DataFrame({"A":[1,2,3],"B":[1/4,1/5,1/6]})
ax = df.plot(secondary_y=['B'])

lines = np.array([axes.lines for axes in ax.figure.axes]).flatten()
print(lines)

For the purpose of creating a single legend you may however just use a figure legend,

import pandas as pd
import matplotlib.pyplot as plt

df = pd.DataFrame({"A":[1,2,3],"B":[1/4,1/5,1/6]})
ax = df.plot(secondary_y=['B'], legend=False)

ax.figure.legend()
plt.show()