4.12. DataFrame Alter

4.12.1. Add Rows and Columns

Code 4.89. Add Column

import pandas as pd

df = pd.DataFrame({
    'A': [10, 11, 12],
    'B': [20, 21, 22],
    'C': [30, 31, 32]})

df
#     A   B   C
# 0  10  20  30
# 1  11  21  31
# 2  12  22  32

df['X'] = ['a', 'b', 'c']
#     A   B   C  X
# 0  10  20  30  a
# 1  11  21  31  b
# 2  12  22  32  c

df['X'] = ['a', 'b']
# Traceback (most recent call last):
# ValueError: Length of values does not match length of index

df['X'] = ['a', 'b', 'c', 'd']
# Traceback (most recent call last):
# ValueError: Length of values does not match length of index

df['Z'] = np.arange(3.0)
#     A   B   C    Z
# 0  10  20  30  0.0
# 1  11  21  31  1.0
# 2  12  22  32  2.0

4.12.2. Drop Rows and Columns

• Works with inplace=True

Code 4.90. Drop Column

import pandas as pd

df = pd.DataFrame({
    'A': [10, 11, 12],
    'B': [20, 21, 22],
    'C': [30, 31, 32]})

df
#     A   B   C
# 0  10  20  30
# 1  11  21  31
# 2  12  22  32

df.drop('A', axis='columns')
#     B   C
# 0  20  30
# 1  21  31
# 2  22  32

df.drop(columns='A')
#     B   C
# 0  20  30
# 1  21  31
# 2  22  32

df.drop(columns=['A', 'B'])
#     C
# 0  30
# 1  31
# 2  32

Code 4.91. Drop Row

import pandas as pd

df = pd.DataFrame({
    'A': [10, 11, 12],
    'B': [20, 21, 22],
    'C': [30, 31, 32]})

df
#     A   B   C
# 0  10  20  30
# 1  11  21  31
# 2  12  22  32

df.drop(1)
#     A   B   C
# 0  10  20  30
# 2  12  22  32

df.drop([0, 2])
#     A   B   C
# 1  11  21  31

rows = df1[:2].index
df.drop(rows)
#     A   B   C
# 2  12  22  32

Code 4.92. Drop from Timeseries

import pandas as pd
import numpy as np
np.random.seed(0)

df = pd.DataFrame(
    columns = ['Morning', 'Noon', 'Evening', 'Midnight'],
    index = pd.date_range('1999-12-30', periods=7),
    data = np.random.randn(7, 4))

df
#              Morning      Noon   Evening  Midnight
# 1999-12-30  1.764052  0.400157  0.978738  2.240893
# 1999-12-31  1.867558 -0.977278  0.950088 -0.151357
# 2000-01-01 -0.103219  0.410599  0.144044  1.454274
# 2000-01-02  0.761038  0.121675  0.443863  0.333674
# 2000-01-03  1.494079 -0.205158  0.313068 -0.854096
# 2000-01-04 -2.552990  0.653619  0.864436 -0.742165
# 2000-01-05  2.269755 -1.454366  0.045759 -0.187184

df.drop('1999-12-30')
# Traceback (most recent call last):
# KeyError: "['1999-12-30'] not found in axis"

df.drop(pd.Timestamp('1999-12-30'))
#              Morning      Noon   Evening  Midnight
# 1999-12-30  1.764052  0.400157  0.978738  2.240893
# 1999-12-31  1.867558 -0.977278  0.950088 -0.151357
# 2000-01-01 -0.103219  0.410599  0.144044  1.454274
# 2000-01-02  0.761038  0.121675  0.443863  0.333674
# 2000-01-03  1.494079 -0.205158  0.313068 -0.854096
# 2000-01-04 -2.552990  0.653619  0.864436 -0.742165
# 2000-01-05  2.269755 -1.454366  0.045759 -0.187184

4.12.3. Transpose

• df.transpose() or df.T

• df.transpose() is preferred

import pandas as pd

df = pd.DataFrame({
    'A': [10, 11, 12],
    'B': [20, 21, 22],
    'C': [30, 31, 32]})

df
#     A   B   C
# 0  10  20  30
# 1  11  21  31
# 2  12  22  32

df.transpose()
#     0   1   2
# A  10  11  12
# B  20  21  22
# C  30  31  32

df.T
#     0   1   2
# A  10  11  12
# B  20  21  22
# C  30  31  32

import pandas as pd

df = pd.DataFrame({
    'A': [10, 11, 12],
    'B': [20, 21, 22],
    'C': [30, 31, 32]})

df['A']         # will select column A
df['B']         # will select column B
df['C']         # will select column C

df.A            # will select column A
df.B            # will select column B
df.C            # will select column C

df.T            # will transpose data
df.transpose()  # will transpose data

import pandas as pd

df = pd.DataFrame({
    'R': [10, 11, 12],
    'S': [20, 21, 22],
    'T': [30, 31, 32]})

df['R']         # will select column R
df['S']         # will select column S
df['T']         # will select column T

df.R            # will select column R
df.S            # will select column S
df.T            # will transpose data

df.transpose()  # will transpose data

4.12.4. Assignments

Todo

Create assignments