Example:

import pandas as pd

d = { 'one' : pd. Series ([ 1 , 2 , 3 ], index=[ 'a' , 'b' , 'c' ]),

   'two' : pd. Series ([ 1 , 2 , 3 , 4 ], index=[ 'a' , 'b' , 'c' , 'd' ])}

df = pd. DataFrame ( d)

print df [ 'one' ]

Its output is as follows −

a     1.0

b     2.0

c     3.0

d     NaN

Name: one, dtype: float64

Column Addition:

We will understand this by adding a new column to an existing data frame.

Example:

import pandas as pd

d = { 'one' : pd. Series ([ 1 , 2 , 3 ], index=[ 'a' , 'b' , 'c' ]),

   'two' : pd. Series ([ 1 , 2 , 3 , 4 ], index=[ 'a' , 'b' , 'c' , 'd' ])}

df = pd. DataFrame ( d)

# Adding a new column to an existing DataFrame object with column label by passing new series

print ( "Adding a new column by passing as Series:" )

df[ 'three' ]= pd. Series ([ 10 , 20 , 30 ], index=[ 'a' , 'b' , 'c' ])

print df

print ( "Adding a new column using the existing columns in DataFrame:" )

df[ 'four' ]= df[ 'one' ]+ df[ 'three' ]

print df

Its output is as follows −

Adding a new column by passing as Series:

     one   two   three

a    1.0    1    10.0

b    2.0    2    20.0

c    3.0    3    30.0

d    NaN    4    NaN

Adding a new column using the existing columns in DataFrame:

      one   two   three    four

a     1.0    1    10.0     11.0

b     2.0    2    20.0     22.0

c     3.0    3    30.0     33.0

d     NaN    4     NaN     NaN

Column Deletion:

Columns can be deleted or popped; let us take an example to understand how.

Example:

# Using the previous DataFrame, we will delete a column

# using del function

import pandas as pd

d = { 'one' : pd. Series ([ 1 , 2 , 3 ], index=[ 'a' , 'b' , 'c' ]),

   'two' : pd. Series ([ 1 , 2 , 3 , 4 ], index=[ 'a' , 'b' , 'c' , 'd' ]),

   'three' : pd. Series ([ 10 , 20 , 30 ], index=[ 'a' , 'b' , 'c' ])}

df = pd. DataFrame ( d)

print ( "Our dataframe is:" )

print df

# using del function

print ( "Deleting the first column using DEL function:" )

del df[ 'one' ]

print df

# using pop function

print ( "Deleting another column using POP function:" )

df. pop( 'two' )

print df

Its output is as follows −

Our dataframe is:

      one   three  two

a     1.0    10.0   1

b     2.0    20.0   2

c     3.0    30.0   3

d     NaN     NaN   4

Deleting the first column using DEL function:

      three    two

a     10.0     1

b     20.0     2

c     30.0     3

d     NaN      4

Deleting another column using POP function:

   three

a  10.0

b  20.0

c  30.0

d  NaN

Row Selection, Addition, and Deletion:

We will now understand row selection, addition and deletion through examples. Let us begin with the concept of selection.

Selection by Label:

Rows can be selected by passing row label to a loc  function.