How to plot Bar Graph in Python using CSV file?

Last Updated : 25 Feb, 2021

CSV stands for “comma separated values”, that means the values are distinguished by putting commas and newline characters. A CSV file provides a table like format that can be read by almost every spreadsheet reader like Microsoft Excel and Google Spreadsheet.

A Bar Graph uses labels and values where label is the name of a particular bar and value represent the height of the bar. A Bar Graph is commonly used in data analytics where we want to compare the data and extract the most common or highest groups.

In this post, we will learn how to plot a bar graph using a CSV file. There are plenty of modules available to read a .csv file like csv, pandas, etc. But in this post we will manually read the .csv file to get an idea of how things work.

Functions Used

Pandas read_csv() function is used to read a csv file.

Syntax:

read_csv(“file path”)

Matplotlib’s bar() function is used to create a bar graph

Syntax:

plt.bar(x, height, width, bottom, align)

Method 1: Using pandas

Approach

Import module
Read file using read_csv() function
Plot bar graph
Display graph

Example:

Dataset in use: Click here

Python3

# Import the necessary modules 
import matplotlib.pyplot as plt 
import pandas as pd 
  
  
# Initialize the lists for X and Y 
data = pd.read_csv('C:\\Users\\Vanshi\\Desktop\\data.csv') 
  
df = pd.DataFrame(data) 
  
X = list(df.iloc[:, 0]) 
Y = list(df.iloc[:, 1]) 
  
# Plot the data using bar() method 
plt.bar(X, Y, color='g') 
plt.title("Students over 11 Years") 
plt.xlabel("Years") 
plt.ylabel("Number of Students") 
  
# Show the plot 
plt.show() 

Output:

Method 2: Using Matplotlib

Approach

Import module
Open file
Read data
Plot bar graph
Display graph

Program:

Dataset in use: Click here to download this file.

Python3

# Import the modules 
import matplotlib.pyplot as plt 
  
# Initialize a dictionary for months 
data = dict() 
  
# Read the data 
with open('electronics.csv', 'r') as f: 
    for line in f.readlines(): 
        
        # Store each line in the dictionary 
        month, item, quantity = line.split(',') 
          
        if month not in data: 
            data[month] = [] 
        data[month].append((item, int(quantity))) 
  
# Position of each subplot where 221 means 2 row, 
# 2 columns, 1st index 
positions = [221, 222, 223, 224] 
  
# Colors to distinguish the plot 
colors = ['r', 'g', 'b', 'y'] 
  
# Plot the subgraphs 
for i, l in enumerate(data.keys()): 
    plt.subplot(positions[i]) 
    data_i = dict(data[l]) 
    plt.bar(data_i.keys(), data_i.values(), color=colors[i]) 
    plt.xlabel(l) 
  
# Show the plots 
plt.show() 

Output:

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Practice Tags :

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How to plot Bar Graph in Python using CSV file?

Functions Used

Method 1: Using pandas

Python3

Method 2: Using Matplotlib

Python3

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