Selecting Columns in a Pandas DataFrame - Examples
Select Column of Pandas DataFrame
You can select a column from Pandas DataFrame using dot notation or either with brackets.
Syntax
# Select column using dot operator
a = myDataframe.column_name
# Select column using square brackets
a = myDataframe[coulumn_name]
Selecting a column return Pandas Series.
Video Tutorial
Examples
1. Select a column using Dot Operator
In this example, we will select a column, from pre-initialized dataframe, using dot operator .
. And shall print the column contents and its datatype.
Python Program
import pandas as pd
# Initialize DataFrame
df = pd.DataFrame({'a': [57, 43, 85], 'b': [92, 30, 66]})
# Select column with name 'a'
a = df.a
print('Selected Column\n---------------\n',a,sep='')
print('\n',type(a),sep='')
Output
Selected Column
---------------
0 57
1 43
2 85
Name: a, dtype: int64
<class 'pandas.core.series.Series'>
The selected column is of class type pandas.core.series.Series
.
2. Select a column using Square Brackets
In this example, we will select a column from Pandas DataFrame using square brackets []
.
Python Program
import pandas as pd
# Initialize DataFrame
df = pd.DataFrame({'a': [57, 43, 85], 'b': [92, 30, 66]})
# Select column with name 'a'
a = df['a']
print('Selected Column\n---------------\n',a,sep='')
print('\n',type(a),sep='')
Output
Selected Column
---------------
0 57
1 43
2 85
Name: a, dtype: int64
<class 'pandas.core.series.Series'>
Selecting a column using square brackets is preferred because in some special scenarios, which we will discuss in the following examples, using dot operator does not work.
3. Select column name with spaces
In this example, we will select column whose name coincides with a function name.
Using dot operator in this scenario throws SyntaxError.
Python Program
import pandas as pd
# Initialize DataFrame
df = pd.DataFrame({'a': [57, 43, 85], 'b': [92, 30, 66], 'sum a b': [149, 73, 151]})
# Select column
a = df.sum a b
print('Selected Column\n---------------\n',a,sep='')
print('\n',type(a),sep='')
Output
File "example1.py", line 7
a = df.sum a b
^
SyntaxError: invalid syntax
Using square brackets will select the column with spaces and returns Series.
Python Program
import pandas as pd
# Initialize DataFrame
df = pd.DataFrame({'a': [57, 43, 85], 'b': [92, 30, 66], 'sum a b': [149, 73, 151]})
# Select column with name 'sum a b'
a = df['sum a b']
print('Selected Column\n---------------\n',a,sep='')
print('\n',type(a),sep='')
Output
Selected Column
---------------
0 149
1 73
2 151
Name: sum a b, dtype: int64
<class 'pandas.core.series.Series'>
Summary
In this tutorial of Python Examples, we learned how to select a column from Pandas DataFrame with the help of well detailed scenarios.