Indexing, selecting, and filtering in Pandas

At times, looking at just one particular subset of data might be beneficial for data analysts to draw conclusions or insights. In such cases, Pandas allows for indexing, selecting, and filtering data to support data analysts to access a particular section of the data set that is relevant and required.

Now, let’s see how to index, select, and filter data in Pandas Series and DataFrames.

Indexing, selecting, and filtering data in Pandas Series

Indexing for Pandas Series uses a labelled index along with the implicit positional index. Following are some of the examples of this behaviour:

Code:

ob1 = Series(np.random.randn(10), index=['a','b','c','d','e','f','g','h','i','j'])
ob1

Output:

a 1.408564

b 0.073118

c -0.261970

d 1.749842

e -0.156697

f -1.444552

g 0.463587

h -0.236253

i -1.641489

j 0.194287

dtype: float64

Code:

ob1[0], ob1['a']

Output:

(1.4085644861854276, 1.4085644861854276)

Slicing gives you a subset of data required for analysis. When slicing with labels, it is essential to remember that both column and row indexes are included in the subset.

The following are some of the examples of this behaviour:

Code:

ob1 = Series(np.random.randn(10), index=['a','b','c','d','e','f','g','h','i','j'])
ob1

Output:

a 0.972519

b -0.301196

c -0.263640

d -0.039523

e -1.145125

f 0.661464

g 0.803230

h -0.346606

i -0.623374

j 1.193851

dtype= float64

Code:

ob1[5], ob1['f']

Output:

(0.661464345493067, 0.661464345493067)

Code:

ob1[0:5]

Output:

a 0.972519

b -0.301196

c -0.263640

d -0.039523

e -1.145125

dtype= float64

Code:

ob1['a':'f']

Output:

a 0.972519

b -0.301196

c -0.263640

d -0.039523

e -1.145125

f 0.661464

dtype= float64

Indexing, selecting, and filtering data in Pandas DataFrames

As we have already seen, we use indexing to retrieve a particular subset of data along the x- and y-axis of DataFrame by passing either the single value or sequence of indexes.
The following examples demonstrate these features again:

Code:

df_states

Output:

Click to enlarge image

Code:

df_states['state']

Output:

Click to enlarge image

Code:

df_states[['state', 'TZ']]

Output:

Click to enlarge image

Next, let’s learn how to align, map, and sort data in Pandas.