Python Pandas DataFrame to draw graphs by using data from MySQL database table

There are three steps in reading data and displaying graph.

Connect to MySQL Database
Get Data using Query and Create DataFrame
Plotting of Graph

Connect to MySQL Database

Using SQLAlchemy we will connect to MySQL database, replace your userid , password and database name ( db_name ) .

from sqlalchemy import create_engine
my_conn = create_engine("mysql+mysqldb://userid:password@localhost/db_name")

We will use the connection string object my_conn in our query.

Get Data using Query and Create DataFrame

SQL query is the first step to get data from MySQL database. This query can be changed to get different type / form of data. We used read_sql() to create the DataFrame using returned data from MySQL table.

query="SELECT class,COUNT( * ) number FROM student GROUP BY class"    
df = pd.read_sql(query,my_conn)
lb= [row for row in df['class']] # Labels of graph

Plotting of Graph

plot=df.plot.pie(title="Students",y='number',
labels=lb,autopct='%1.0f%%')

Full code is here.

import pandas as pd # import Pandas library 
from sqlalchemy import create_engine
my_conn = create_engine("mysql+mysqldb://usrid:password@localhost/my_db")
query="SELECT class,COUNT( * ) number FROM student GROUP BY class"    
df = pd.read_sql(query,my_conn)
lb= [row for row in df['class']] # Labels of graph

plot=df.plot.pie(title="Students ",y='number',labels=lb,autopct='%1.0f%%')

Pie Chart

Using Bar graph

Connection to MySQL and query execution remain same as above code, only the last line is changed to generate the bar graph.

import pandas as pd 
from sqlalchemy import create_engine
my_conn = create_engine("mysql+mysqldb://root:test@localhost/my_tutorial")
query="SELECT class,COUNT(*) number FROM student GROUP BY class"    
df = pd.read_sql(query,my_conn)
plot=df.plot.bar(title="Student Number",x='class');

Bar graph

Horizontal Bar graph

We will plot one Horizontal bar graph by changing the last line only.

plot=df.plot.barh(title="Student Number",x='class');

HBar graph

More than one value in Bar graph

In above code we kept two columns, now we will use three columns. One columns class we will use in y axis, other two columns maximum mark ( max ) and average value ( avg ) will be used to draw the graphs.

Note that only the Query part is changed ( from above code ) here and the DataFrame is having one more column data

import pandas as pd # import Pandas library 
from sqlalchemy import create_engine
my_conn = create_engine("mysql+mysqldb://root:test@localhost/my_tutorial")
query="SELECT class,MAX(mark) max, AVG(mark) avg FROM student GROUP BY class"    
df = pd.read_sql(query,my_conn)
plot=df.plot.bar(title="Student Number",x='class');

Stacked Bar Graph

We will break the number of students in two parts based on gender ( male , female ) and create stacked bar graph ( Note the option stacked=True ). Query is also changed to include GROUP BY and CASE.

import pandas as pd # import Pandas library 
from sqlalchemy import create_engine
my_conn = create_engine("mysql+mysqldb://root:test@localhost/my_tutorial")
query="SELECT class,\
sum(CASE WHEN gender ='male' THEN 1 ELSE 0 END) as Male,\
sum(CASE WHEN gender ='Female' THEN 1 ELSE 0 END) as Female\
 FROM student group by class"    
df = pd.read_sql(query,my_conn)
plot=df.plot.bar(title="Student Number",x='class',stacked=True);

Using Line Graph

Only the last line is changed ( from the above code given for simple bar graph) .

plot=df.plot.line(title="Student Number",x='class',y='number')

Line Plot

Density graph

Using mark column we will create density graph. The query and drawing graph is only shown here as the library and connection string is same as given above.

query="SELECT mark FROM student"    
df = pd.read_sql(query,my_conn)
plot=df.plot.density();

Density

Scatter graph

Two numeric columns are used for this graph.

query="SELECT COUNT( * ) number,avg(mark) avg FROM student GROUP BY class"    
df = pd.read_sql(query,my_conn)
plot=df.plot.scatter(title="Average Vs Number ",x='avg',y='number')

Scatter

Saving graph as image

plot=df.plot.pie(title="Students",y='number',
labels=lb,autopct='%1.0f%%')
fig = plot.get_figure()
fig.savefig("D:\\my_data\\output2.png")

Pandas plot plot.barh()

Numpy arrays Python & MySQL Python- Tutorials

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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