Python for Data Science

Chapter 2 - Data Preparation Basics

Segment 4 - Concatenating and transforming data

import numpy as np
import pandas as pd

from pandas import Series, DataFrame

DF_obj = pd.DataFrame(np.arange(36).reshape(6,6))
DF_obj

	0	1	2	3	4	5
0	0	1	2	3	4	5
1	6	7	8	9	10	11
2	12	13	14	15	16	17
3	18	19	20	21	22	23
4	24	25	26	27	28	29
5	30	31	32	33	34	35

DF_obj_2 = pd.DataFrame(np.arange(15).reshape(5,3))
DF_obj_2

	0	1	2
0	0	1	2
1	3	4	5
2	6	7	8
3	9	10	11
4	12	13	14

Concatenating data

pd.concat([DF_obj,DF_obj_2],axis=1)

	0	1	2	3	4	5	0	1	2
0	0	1	2	3	4	5	0.0	1.0	2.0
1	6	7	8	9	10	11	3.0	4.0	5.0
2	12	13	14	15	16	17	6.0	7.0	8.0
3	18	19	20	21	22	23	9.0	10.0	11.0
4	24	25	26	27	28	29	12.0	13.0	14.0
5	30	31	32	33	34	35	NaN	NaN	NaN

pd.concat([DF_obj,DF_obj_2])

	0	1	2	3	4	5
0	0	1	2	3.0	4.0	5.0
1	6	7	8	9.0	10.0	11.0
2	12	13	14	15.0	16.0	17.0
3	18	19	20	21.0	22.0	23.0
4	24	25	26	27.0	28.0	29.0
5	30	31	32	33.0	34.0	35.0
0	0	1	2	NaN	NaN	NaN
1	3	4	5	NaN	NaN	NaN
2	6	7	8	NaN	NaN	NaN
3	9	10	11	NaN	NaN	NaN
4	12	13	14	NaN	NaN	NaN

Transforming data

Dropping data

DF_obj.drop([0,2])

	0	1	2	3	4	5
1	6	7	8	9	10	11
3	18	19	20	21	22	23
4	24	25	26	27	28	29
5	30	31	32	33	34	35

DF_obj.drop([0,2],axis=1)

	1	3	4	5
0	1	3	4	5
1	7	9	10	11
2	13	15	16	17
3	19	21	22	23
4	25	27	28	29
5	31	33	34	35

Adding data

series_obj = Series(np.arange(6))
series_obj.name = "added_variable"
series_obj

0    0
1    1
2    2
3    3
4    4
5    5
Name: added_variable, dtype: int64

variable_added = DataFrame.join(DF_obj,series_obj)
variable_added

	0	1	2	3	4	5	added_variable
0	0	1	2	3	4	5	0
1	6	7	8	9	10	11	1
2	12	13	14	15	16	17	2
3	18	19	20	21	22	23	3
4	24	25	26	27	28	29	4
5	30	31	32	33	34	35	5

added_datatable = variable_added.append(variable_added, ignore_index=False)
added_datatable

	0	1	2	3	4	5	added_variable
0	0	1	2	3	4	5	0
1	6	7	8	9	10	11	1
2	12	13	14	15	16	17	2
3	18	19	20	21	22	23	3
4	24	25	26	27	28	29	4
5	30	31	32	33	34	35	5
0	0	1	2	3	4	5	0
1	6	7	8	9	10	11	1
2	12	13	14	15	16	17	2
3	18	19	20	21	22	23	3
4	24	25	26	27	28	29	4
5	30	31	32	33	34	35	5

added_datatable = variable_added.append(variable_added, ignore_index=True)
added_datatable

	0	1	2	3	4	5	added_variable
0	0	1	2	3	4	5	0
1	6	7	8	9	10	11	1
2	12	13	14	15	16	17	2
3	18	19	20	21	22	23	3
4	24	25	26	27	28	29	4
5	30	31	32	33	34	35	5
6	0	1	2	3	4	5	0
7	6	7	8	9	10	11	1
8	12	13	14	15	16	17	2
9	18	19	20	21	22	23	3
10	24	25	26	27	28	29	4
11	30	31	32	33	34	35	5

Sorting data

DF_sorted = DF_obj.sort_values(by=(5),ascending=[False])
DF_sorted

	0	1	2	3	4	5
5	30	31	32	33	34	35
4	24	25	26	27	28	29
3	18	19	20	21	22	23
2	12	13	14	15	16	17
1	6	7	8	9	10	11
0	0	1	2	3	4	5