Matplotlib savefig size

Question

Hello I made a graph with Matplotlib in python and as you can see here it doesn't display well. I tried solutions from this but it change nothing.

# plot
plt.plot('x', 'data', data=df, linestyle='-', marker='o')
buf = io.BytesIO()
plt.savefig(buf, format='png')
buf.seek(0)

As you can see here with plt.show() it's ok