Creating Series from list and dictionary in Pandas - Practice Exercises

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Series created from list with index

What is the output of this code snippet?

Pandas

import pandas as pd
s = pd.Series([10, 20, 30], index=['a', 'b', 'c'])
print(s['b'])

A 10

B KeyError

C 30

D 20

💡 Hint

Remember that the index labels are used to access values in a Series.

The Series is created with index labels 'a', 'b', 'c'. Accessing s['b'] returns the value 20.

❓ data_output

intermediate

Length of Series created from dictionary

How many items are in the Series created from this dictionary?

Pandas

import pandas as pd
d = {'x': 1, 'y': 2, 'z': 3}
s = pd.Series(d)
print(len(s))

A 3

B 2

C 1

D 0

💡 Hint

Each key-value pair in the dictionary becomes one item in the Series.

The dictionary has 3 key-value pairs, so the Series has length 3.

🔧 Debug

advanced

Error raised when creating Series with mismatched index

What error does this code raise?

Pandas

import pandas as pd
s = pd.Series([1, 2], index=['a', 'b', 'c'])

A ValueError: Length of passed values is 2, index implies 3

B TypeError: unsupported operand type(s)

C KeyError: 'c'

D No error, creates Series with NaN

💡 Hint

Check if the length of data matches the length of the index.

The data list has length 2 but the index has length 3, causing a ValueError.

🧠 Conceptual

advanced

Behavior of Series when dictionary keys are not strings

What will be the index of the Series created from this dictionary?

Pandas

import pandas as pd
d = {1: 'a', 2: 'b', 3: 'c'}
s = pd.Series(d)
print(s.index.tolist())

A ['1', '2', '3']

B [1, 2, 3]

C ['a', 'b', 'c']

D RangeIndex(start=0, stop=3, step=1)

💡 Hint

Dictionary keys become the index labels as they are.

The Series index uses the dictionary keys as labels, so the index is [1, 2, 3].

🚀 Application

expert

Creating Series with partial index from dictionary

Given the dictionary and index below, what is the output of the Series?

Pandas

import pandas as pd
d = {'a': 100, 'b': 200, 'c': 300}
index = ['a', 'c', 'd']
s = pd.Series(d, index=index)
print(s)

A KeyError: 'd'

B

a    100
b    200
c    300
d    NaN
dtype: float64

C

a    100.0
c    300.0
d      NaN
dtype: float64

D

a    100
c    300
d    0
dtype: int64

💡 Hint

When index has labels not in dictionary keys, pandas fills with NaN.

The Series uses the given index. 'd' is missing in dictionary, so its value is NaN.