Plotting normal distribution with percentage or counts of data for each S.D

Question

l = {31.2: 1, 35.1: 4, 39.0: 13, 42.9: 33, 46.8: 115, 50.7: 271, 54.6: 363, 58.5: 381, 62.4: 379, 66.3: 370, 70.2: 256, 74.1: 47, 78.0: 2}
# convert the dictionary to a list
l_list = [k for k, v in l.items() for _ in range(v)]

I desire the normal distribution curve fit to the above data along with the number of samples printed on each area similar to shown in below figure.

Answer 1

Here is a way to calculate and draw a gaussian normal that fits the data. Note that the data were already grouped together beforehand, so the true mean and standard deviation can't be calculated anymore.

import numpy as np
import matplotlib.pyplot as plt
from scipy.stats import gaussian_kde, norm

l = {31.2: 1, 35.1: 4, 39.0: 13, 42.9: 33, 46.8: 115, 50.7: 271, 54.6: 363, 58.5: 381, 62.4: 379, 66.3: 370, 70.2: 256, 74.1: 47, 78.0: 2}
# convert the dictionary to a list
l_array = np.array( [k for k, v in l.items() for _ in range(v)])


s = sum(l.values())
bin_width = 3.9
bin_centers = list(l.keys())
heights = [v/s/bin_width for v in l.values()]
plt.bar(bin_centers, heights, width=bin_width*0.9, color='dodgerblue', label='histogram')
for c, h, v in zip(bin_centers, heights, l.values()):
    plt.text(c, h, v, ha='center', va='bottom')
plt.xticks(bin_centers)
mean = l_array.mean()
sdev = l_array.std()
for i in range(-3, 4):
    plt.axvline(mean+i*sdev, color='limegreen', ls='--', lw=2, label='mean + i*sdev' if i == 0 else None)

x = np.linspace(mean-4*sdev, mean+4*sdev, 500)
plt.plot(x, norm.pdf(x, mean, sdev), color='orange', lw=3, label='gaussian normal')
plt.autoscale(enable=True, axis='x', tight=True)
plt.legend()
plt.show()