A population pyramid is a graph that shows the age and gender distribution of a given population. It’s useful for understanding the composition of a population and the trend in population growth.
This tutorial explains how to create the following population pyramid in Python:
Population Pyramid in Python
Suppose we have the following dataset that displays the total population of males and females by age group for a given country:
#import libraries import numpy as np import pandas as pd import matplotlib.pyplot as plt #create dataframe df = pd.DataFrame({'Age': ['0-9','10-19','20-29','30-39','40-49','50-59','60-69','70-79','80-89','90+'], 'Male': [9000, 14000, 22000, 26000, 34000, 32000, 29000, 22000, 14000, 3000], 'Female': [8000, 15000, 19000, 28000, 35000, 34000, 28000, 24000, 17000, 5000]}) #view dataframe df Age Male Female 0 0-9 9000 8000 1 10-19 14000 15000 2 20-29 22000 19000 3 30-39 26000 28000 4 40-49 34000 35000 5 50-59 32000 34000 6 60-69 29000 28000 7 70-79 22000 24000 8 80-89 14000 17000 9 90+ 3000 5000
We can use the following code to create a population pyramid for the data:
#define x and y limits y = range(0, len(df)) x_male = df['Male'] x_female = df['Female'] #define plot parameters fig, axes = plt.subplots(ncols=2, sharey=True, figsize=(9, 6)) #specify background color and plot title fig.patch.set_facecolor('xkcd:light grey') plt.figtext(.5,.9,"Population Pyramid ", fontsize=15, ha='center') #define male and female bars axes[0].barh(y, x_male, align='center', color='royalblue') axes[0].set(title='Males') axes[1].barh(y, x_female, align='center', color='lightpink') axes[1].set(title='Females') #adjust grid parameters and specify labels for y-axis axes[1].grid() axes[0].set(yticks=y, yticklabels=df['Age']) axes[0].invert_xaxis() axes[0].grid() #display plot plt.show()
From the plot we can see that the distribution of males and females is fairly symmetrical, with most of the population falling in the middle-age brackets. By simply looking at this one plot, we can get a decent idea about the demographics of this particular country.
Note that you can adjust the colors of the plot background and the individual bars by specifying colors from the matplotlib color list.
For example, we could specify ‘hotpink’ and ‘dodgerblue’ to be used with a ‘beige’ background:
fig.patch.set_facecolor('xkcd:beige')
axes[0].barh(y, x_male, align='center', color='dodgerblue')
axes[1].barh(y, x_female, align='center', color='hotpink')
plt.show()
Feel free to modify the color scheme based on what you think looks best.