Using variables and equations matplotlib legend

Question

I want to use the variable DelG_Zero in the legend. I tried the following (by referring to previous stackoverflow posts) and did not work. How do I resolve this?

Error message:

  File "<ipython-input-187-b5fccd6494bb>", line 13, in <module>
    plt.legend([r'$\Delta G_0 = {}$',r'$\Delta G_0={}$',r'$\Delta G_0={}$'].format([DelG_Zero[0],DelG_Zero[1],DelG_Zero[2]]),fontsize=12)

AttributeError: 'list' object has no attribute 'format'

Code:

import numpy as np
import matplotlib.pyplot as plt

DelG_Zero =[2.8,5,7]

fig = plt.figure()
lines = plt.plot(range(10), np.random.randn(10), range(10), np.random.randn(10), range(10), np.random.randn(10))
plt.legend([r'$\Delta G_0 = {}$',r'$\Delta G_0={}$',r'$\Delta G_0={}$'].format([DelG_Zero[0],DelG_Zero[1],DelG_Zero[2]]),fontsize=12)

plt.show()

Answer 1

You are calling .format on the list of strings, not each string itself. A list doesn't have a .format method, so an AttributeError is raised.

To solve this, you should directly format the strings:

plt.legend([r"$\Delta G_0 = {}$".format(x) for x in DelG_Zero], fontsize=12)

If you're using Python 3.6 or later, you can use f-strings for slightly cleaner syntax:

plt.legend([rf"$\Delta G_0 = {x}$" for x in DelG_Zero], fontsize=12)