I don't know how to correct this

x_axis=df['month_number']
y_axis=df['bathingsoap']
plt.bar(x_axis,y_axis,label='bathsoap sales')
plt.xlabel('Months')
plt.ylabel('Soap Sales')
plt.title('bathingsoap sales data')
plt.figure(figsize=(5,5))
plt.legend()
plt.show()

plt.legend() elements are automatically determined or you can list the labels specifically like:

ax.legend([line1, line2, line3], ['label1', 'label2', 'label3'])

It would be better if you specified what you wanted in the legend (label text) as noted in the example above rather than just calling plt.legend(). Also, check your data, as the error suggests there’s an “__” somewhere in that array.

This might be of some help:
https://matplotlib.org/stable/api/_as_gen/matplotlib.pyplot.legend.html

And, here’s more of an in-depth explanation of artists:
https://dev.to/skotaro/artist-in-matplotlib—something-i-wanted-to-know-before-spending-tremendous-hours-on-googling-how-tos–31oo

I read the link and i put the handles but this is what it says