[Python] How to create a table from list (basic operation of table creation / change of matrix name)

[Python] How to create a table from list (basic operation of table creation / change of matrix name)

About the basic operation of creating a table in python. A summary of how to create and operate a table based on one list data for easy understanding.

Use pandas DataFrame to create the table.

Official Page

1. [One-column table](# 1 One-column table)
2. [Create Table](# 1-1 Create Table)
3. [Rename column](# 1-2 Rename column)
4. [Rename line](# 1-3 Rename line)
5. [Change matrix name at the same time](# 1-4 Matrix name changed at the same time)
6. [Multi-column table](# 2 Multi-column table)
7. [Join in list state](Join in #list state)
8. [Make a table and then join](# Make a table and then join)
9. Join 4 Tables (# Join 4 Tables)

listA = ['AAA', 'BBB', 'CCC', 'DDD', 'EEE']

pd.DataFrame (array) └ "pd": pandas Abbreviation. pd import └ "DataFrame": 2D table data

Creating a table

import pandas as pd

listA = ['AAA', 'BBB', 'CCC', 'DDD']
df1 = pd.DataFrame(listA)
df1

#output
	0
0	AAA
1	BBB
2	CCC
3	DDD

-The array is output as a table ・ The first column is the heading (index number from 0) ・ The first row is the column name (index number from 0)

Creating a table (directly)

import pandas as pd
pd.DataFrame(['AAA', 'BBB', 'CCC', 'DDD'])

#output
	0
0	AAA
1	BBB
2	CCC
3	DDD

① Designated when creating the table

Specify columns = ['AAA'] in the DataFrame option. └ "AAA": Column name (optional)

Rename column

import pandas as pd

listA = ['AAA', 'BBB', 'CCC', 'DDD']
df2 = pd.DataFrame(listA, columns=['Ah ah'])
df2

#output
Ah ah
0	AAA
1	BBB
2	CCC
3	DDD

• None (columns ='Ah') will result in an error.

df.columns = ['AAA'] └ "df": Table data └ ".columns": Get column names └ "AAA": Column name to be assigned

Assign using the columns method.

• The value to be assigned is [] required. Otherwise, an error will occur.

Rename column (later)

df1.columns = ['Ah ah']
df1

#output
Ah ah
0	AAA
1	BBB
2	CCC
3	DDD

rename can specify which column name to change and how. {Original column name: Modified column name}

Change with rename method

df1.rename(columns={0:'Ah ah'})

#output
Ah ah
0	AAA
1	BBB
2	CCC
3	DDD

① Designated when creating the table ② Change later ②-1. index method ②-2. rename method

① Designated when creating the table

Specify ʻindex = ['AAA','BBB' ,,,,]` in the DataFrame option. └ "AAA" "BBB": Line name (optional) └ Either character string or numerical value can be specified

• The number of lines and the number of elements specified by index must match. Error if there are many or few.

** ▼ Specify by character string **

Rename column (character string)

import pandas as pd

listA = ['AAA', 'BBB', 'CCC', 'DDD']
df1 = pd.DataFrame(listA, index=['111','222','333','444'])
df1

#output
	0
111	AAA
222	BBB
333	CCC
444	DDD

Column name change (numerical value)

import pandas as pd

listA = ['AAA', 'BBB', 'CCC', 'DDD']
df1 = pd.DataFrame(listA, index=[111,22.2,3.33,444])
df1

#output
	0
111.00	AAA
22.20	BBB
3.33	CCC
444.00	DDD

Column name change (numerical value)

import pandas as pd

listA = ['AAA', 'BBB', 'CCC', 'DDD']
indexA = ['111','222','333','444']

df1 = pd.DataFrame(listA, index=indexA)
df1

#output
	0
111	AAA
222	BBB
333	CCC
444	DDD

Specify df.index = ['AAA','BBB' ,,,,]. └ "AAA" "BBB": Line name (optional) └ Both character string and numerical value can be specified

• The number of lines and the number of elements specified by index must match. Error if there are many or few.

Change index name later

df1.index = ['111','222','333','444']
df1

#output
	0
111	AAA
222	BBB
333	CCC
444	DDD

rename can specify which column name to change and how. rename = (index = {original line name: changed line name})

Change with rename method

df1.rename(index={1:'111',3:'333'})

#output
	0
0	AAA
111	BBB
2	CCC
333	DDD

① Designated when creating the table ② Change later ②-1. index method ②-2. rename method

① Designated when creating the table

With DataFrame options columns=['AAA','BBB',,,,] index=['aaa','bbb',,,,] Is specified. └ "AAA" "BBB": Column name (optional) └ "aaa" "bbb": Line name (optional)

• The number of matrices and the number of elements specified by columns and index must match. Error if there are many or few.

Specify a matrix

import pandas as pd

listA = ['AAA', 'BBB', 'CCC', 'DDD']
df1 = pd.DataFrame(listA, columns=['Ah ah'], index=['111','222','333','444'])
df1


#output
Ah ah
111	AAA
222	BBB
333	CCC
444	DDD

Specify a matrix (variable)

import pandas as pd

listA = ['AAA', 'BBB', 'CCC', 'DDD']
cols = ['Ah ah']
inds = ['111','222','333','444']

df1 = pd.DataFrame(listA, columns=cols, index=inds)
df1


#output
Ah ah
111	AAA
222	BBB
333	CCC
444	DDD

rename can specify which column name to change and how. rename (index = {original row name: modified row name}, columns = {original column name: modified column name})

• Both index and columns should be described in () of the same rename. If you divide it into two lines, only one will be reflected.

Specify matrix (rename method)

import pandas as pd

listA = ['AAA', 'BBB', 'CCC', 'DDD']
df1 = pd.DataFrame(listA)

df1.rename(columns={0:'Good'}, index={1:'111', 3:'333', 4:'444'})


#output
Good
0	AAA
111	BBB
2	CCC
333	DDD

Create a multi-column table from multiple lists.

Combine two lists.

• How to join one row at a time

list

listA = ['AAA', 'BBB', 'CCC', 'DDD']
listB = ['EEE', 'FFF', 'GGG', 'HHH']

Method ① Combine in the state of list ② Make a table and then join

① Combine in the state of list

1. Make list A a table.
2. Specify the column name and element to add.

df['aaa'] = ['AAA', 'BBB',,,] └ "df": Original table └ "aaa": Column name to be added (numerical value is also acceptable) └ "AAA" "BBB": Column elements

• If the number of elements in the original table and the number of elements in the list to be added are different, an error will occur.

Add column

import pandas as pd

listA = ['AAA', 'BBB', 'CCC', 'DDD']
df1= pd.DataFrame(listA)

df1[1] =  ['EEE', 'FFF', 'GGG', 'HHH']
df1

#output
	0	1
0	AAA	EEE
1	BBB	FFF
2	CCC	GGG
3	DDD	HHH

Error if the number of elements is different

import pandas as pd

listA = ['AAA', 'BBB', 'CCC', 'DDD']
df1= pd.DataFrame(listA)

df1[1] =  ['EEE', 'FFF', 'GGG']
df1

#output
# ValueError: Length of values does not match length of index

1. Make list A a table.
2. Turn listB into a table.
3. Specify the column name in the table of listA and the table of listB in the element. df['aaa'] = dfB └ "df": Original table └ "aaa": Column name to be added (numerical value is also acceptable) └ "AAA" "BBB": Column elements

• If the number of elements in the original table and the number of elements in the list to be added are different, an error will occur.

Add column

import pandas as pd

listA = ['AAA', 'BBB', 'CCC', 'DDD']
dfA= pd.DataFrame(listA)

listB =['EEE', 'FFF', 'GGG', 'HHH']
dfB= pd.DataFrame(listB)

dfA['1'] = dfB
dfA

#output
	0	1
0	AAA	EEE
1	BBB	FFF
2	CCC	GGG
3	DDD	HHH

In the case of "+"

import pandas as pd

listA = ['AAA', 'BBB', 'CCC', 'DDD']
dfA= pd.DataFrame(listA)

listB =['EEE', 'FFF', 'GGG', 'HHH']
dfB= pd.DataFrame(listB)

dfA + dfB

#output
	0
0	AAAEEE
1	BBBFFF
2	CCCGGG
3	DDDHHH

Original table

listA = ['AAA', 'BBB', 'CCC', 'DDD']
listB = ['EEE', 'FFF', 'GGG', 'HHH']
listC = ['III', 'JJJ', 'KKK', 'LLL']
listD = ['MMM', 'NNN', 'OOO', 'PPP']

Join table

import pandas as pd

listA = ['AAA', 'BBB', 'CCC', 'DDD']
listB = ['EEE', 'FFF', 'GGG', 'HHH']
listC = ['III', 'JJJ', 'KKK', 'LLL']
listD = ['MMM', 'NNN', 'OOO', 'PPP']

dfA = pd.DataFrame(listA)
dfA[1] = listB
dfA[2] = listC
dfA[3] = listD

dfA


#output
	0	1	2	3
0	AAA	EEE	III	MMM
1	BBB	FFF	JJJ	NNN
2	CCC	GGG	KKK	OOO
3	DDD	HHH	LLL	PPP