Series indexing and selection in Data Analysis Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a Pandas Series?

A Pandas Series is like a list with labels. It holds data and each item has an index label to find it easily.

beginner

How do you select a single value from a Series using its label?

Use series[label] to get the value at that label. For example, series['a'] gets the value where the index is 'a'.

intermediate

What is the difference between loc and iloc in Series selection?

loc selects data by label, while iloc selects data by integer position (like counting from 0).

beginner

How can you select multiple values from a Series?

You can pass a list of labels or positions inside loc or iloc. For example, series.loc[['a', 'b']] or series.iloc[[0, 1]].

intermediate

What happens if you try to select a label that does not exist in a Series?

Pandas will raise a KeyError because the label is not found in the Series index.

Which method selects data by integer position in a Pandas Series?

A loc

B iloc

C at

D ix

iloc selects data by integer position, counting from 0.

What will series['x'] do if 'x' is not an index label in the Series?

A Return None

B Return NaN

C Raise a KeyError

D Return the first value

Accessing a non-existent label raises a KeyError.

How do you select the first three elements of a Series by position?

A series.iloc[:3]

B series[:3]

C series.loc[:3]

D series.loc[0:2]

iloc[:3] selects elements at positions 0, 1, and 2.

Which of these is a valid way to select multiple labels from a Series?

A series.loc[['a', 'b']]

B series[['a', 'b']]

C series.iloc['a', 'b']

D series.loc['a', 'b']

Use a list inside loc to select multiple labels.

What type of object is returned when selecting a single value from a Series?

A List

B DataFrame

C Series

D Scalar (single value)

Selecting a single label returns a scalar value, not a Series.

Explain how to select data from a Pandas Series using labels and positions.

Think about how you find items by name versus by order.

Describe what happens when you try to access a label that does not exist in a Series.

What error does Python raise when a key is missing?