Creating a Series

A Series can be born from all sorts of data — a plain list, a NumPy array, a dictionary, even a single value. Every one of them starts with the same import, then a call to pd.Series(...).

Play with the builder below to preview each source, then run the real code in the panels underneath.

Series builder

Pick a source of data — see the code that builds it and the Series it produces.

import pandas as pd
cities = ['Mumbai', 'Delhi', 'Bengaluru', 'Chennai']
s = pd.Series(cities)
print(s)

0Mumbai

1Delhi

2Bengaluru

3Chennai

dtype: object

💡 List: Most common way. Pandas auto-numbers the index from 0.

1Method 1 — The empty Series

Sometimes you need to start with nothing and fill it in later. Calling pd.Series() with no arguments creates an empty Series.

method1_empty.py

import pandas as pd

# Creates an empty Series
empty_s = pd.Series()
print(empty_s)

import pandas as pd

# Creates an empty Series
empty_s = pd.Series()
print(empty_s)

2Method 2 — From a Python list

This is the most common way. Pandas automatically creates a default integer index starting from 0.

method2_list.py

import pandas as pd

# Series from a list of Indian cities
cities = ['Mumbai', 'Delhi', 'Bengaluru', 'Chennai']
s_from_list = pd.Series(cities)
print(s_from_list)

import pandas as pd

# Series from a list of Indian cities
cities = ['Mumbai', 'Delhi', 'Bengaluru', 'Chennai']
s_from_list = pd.Series(cities)
print(s_from_list)

Beyond the default: pass index=... to give every value a meaningful label of your own.

method2_custom_index.py

import pandas as pd

marks = [98, 67, 86, 92]
labels = ['Amit', 'Divya', 'Vinay', 'Sara']
s = pd.Series(data=marks, index=labels)
print(s)

import pandas as pd

marks = [98, 67, 86, 92]
labels = ['Amit', 'Divya', 'Vinay', 'Sara']
s = pd.Series(data=marks, index=labels)
print(s)

Note

The index list must be the same length as the data list — one label per value.

3Method 3 — From a NumPy ndarray

Pandas is built on top of NumPy, so turning an array into a Series is seamless and efficient.

method3_ndarray.py

import pandas as pd
import numpy as np

# Series from a NumPy array of cricket scores
scores = np.array([102, 88, 95, 74])
s_from_ndarray = pd.Series(scores)
print(s_from_ndarray)

import pandas as pd
import numpy as np

# Series from a NumPy array of cricket scores
scores = np.array([102, 88, 95, 74])
s_from_ndarray = pd.Series(scores)
print(s_from_ndarray)

4Method 4 — From a dictionary

This one is powerful: the dictionary's keys automatically become the Series' index labels, and the values become the data.

method4_dict.py

import pandas as pd

# Series from a dictionary of population (in millions)
population = {'Mumbai': 12.5, 'Delhi': 11.0, 'Kolkata': 4.5}
s_from_dict = pd.Series(population)
print(s_from_dict)

import pandas as pd

# Series from a dictionary of population (in millions)
population = {'Mumbai': 12.5, 'Delhi': 11.0, 'Kolkata': 4.5}
s_from_dict = pd.Series(population)
print(s_from_dict)

5Method 5 — From a scalar (single value)

Want a Series where every element is the same? Give a single value — but you must also provide an index, so Pandas knows how many times to repeat it.

method5_scalar.py

import pandas as pd

# The value 'Holiday' repeated for several dates
s_from_scalar = pd.Series(
    'Holiday',
    index=['2025-01-26', '2025-08-15', '2025-10-02']
)
print(s_from_scalar)

import pandas as pd

# The value 'Holiday' repeated for several dates
s_from_scalar = pd.Series(
    'Holiday',
    index=['2025-01-26', '2025-08-15', '2025-10-02']
)
print(s_from_scalar)

Watch Out

Forget the index with a scalar and Pandas has no idea how long the Series should be — you'll get an error. The index does double duty here: it sets both the labels and the length.

6Recap — five ways in

Ways to create a Series

Source	Example	Index you get
Empty	pd.Series()	none (empty)
List	pd.Series([1, 2, 3])	default 0, 1, 2
List + index	pd.Series(data, index=labels)	your labels
NumPy array	pd.Series(np.array([...]))	default 0, 1, 2
Dictionary	pd.Series({'a': 1})	the dict keys
Scalar	pd.Series(9, index=[...])	your labels (required)

Quick Check

You build a Series from a dictionary. What becomes the index?

Quick Check

Which creation method REQUIRES you to pass an index?

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📖 What is a Series?

Data Types & Missing Data 🏷️