Pandas Series Introduction
This is a beginner’s guide of Python pandas Series Tutorial where you will learn what is pandas Series? its features, advantages, and how to use panda Series with sample examples.
Every sample example explained in this tutorial is tested in our development environment and is available for reference.
All pandas Series examples provided in this tutorial are basic, simple, and easy to practice for beginners who are enthusiastic to learn pandas and advance their career in Data Science, analytics, and Machine Learning.
Note: In case you can’t find the pandas Series examples you are looking for on this tutorial page, I would recommend using the Search option from the menu bar to find your tutorial and sample example code, there are hundreds of tutorials in pandas on this website you can learn from.
What is the Pandas Series
Pandas Series is a one-dimensional labeled array capable of holding data of any type (integer, string, float, etc.). It’s similar to a one-dimensional array or a list in Python, but with additional functionalities. Each element in a Pandas Series has a label associated with it, called an index. This index allows for fast and efficient data access and manipulation. Pandas Series can be created from various data structures like lists, dictionaries, NumPy arrays, etc.
Pandas Series vs DataFrame?
- As I explained above, pandas Series is a one-dimensional labeled array of the same data type whereas DataFrame is a 2-dimensional labeled data structure with columns of potentially different types.
- In a DataFrame, each column of data is represented as a pandas Series.
- DataFrame column can have a name/label but, Series cannot have a column name.
- DataFrame can also be converted to Series and single or multiple Series can be converted to a DataFrame. Refer to pandas DataFrame Tutorial for more details and examples on DataFrame.
Syntax of pandas.series()
Following is the syntax of the pandas.series(), which is used to create Pandas Series objects.
# Pandas Series Constructor Syntax
Pandas.series(data,index,dtype,copy)
data– The data to be stored in the Series. It can be a list, ndarray, dictionary, scalar value (like an integer or string), etc.Index– Optional. It allows you to specify the index labels for the Series. If not provided, default integer index labels (0, 1, 2, …) will be used.dtype– Optional. The data type of the Series. If not specified, it will be inferred from the data.copy– Optional. If True, it makes a copy of the data. Default is False.
Create pandas Series
pandas Series can be created in multiple ways, From array, list, dict, and from existing DataFrame.
Create Series using array
Before creating a Series, first, we have to import the NumPy module and use array() function in the program. If the data is ndarray, then the passed index should be in the same length, if the index is not passed the default value is range(n).
# Create Series from array
import pandas as pd
import numpy as np
data = np.array(['python','php','java'])
series = pd.Series(data)
print (series)
# Output:
# 0 python
# 1 php
# 2 java
# dtype: object
Notice that the column doesn’t have a name. And Series also adds an incremental sequence number as Index (first column) by default.
To customize the index of a Pandas Series, you can provide the index parameter when creating the Series using the pd.Series() constructor.
# Create pandas DataFrame with custom index
s2=pd.Series(data=data, index=['r1', 'r2', 'r3'])
print(s2)
# Output:
# r1 python
# r2 php
# r3 java
# dtype: object
Create Series using Dict
A Dict can be used as input. Keys from Dict are used as Index and values are used as a column.
# Create a Dict from a input
data = {'Courses' :"pandas", 'Fees' : 20000, 'Duration' : "30days"}
s2 = pd.Series(data)
print (s2)
# Output:
# Courses pandas
# Fees 20000
# Duration 30days
# dtype: object
Now let’s see how to ignore Index from Dict and add the Index while creating a Series with Dict.
# To See index from Dict and add index while creating a Series.
data = {'Courses' :"pandas", 'Fees' : 20000, 'Duration' : "30days"}
s2 = pd.Series(data, index=['Courses','Course_Fee','Course_Duration'])
print (s2)
Create Series using List
Below is an example of creating DataFrame from List.
# Creating DataFrame from List
data = ['python','php','java']
s2 = pd.Series(data, index=['r1', 'r2','r3'])
print(s2)
# Output:
# r1 python
# r2 php
# r3 java
# dtype:object
Create Empty Series
Sometimes you would require to create an empty Series. you can do so by using its empty constructor.
# Create empty Series
import pandas as pd
s = pd.Series()
print(s)
This shows an empty series.
Convert a Series into a DataFrame
To convert Series into DataFrame, you can use pandas.concat(), pandas.merge(), DataFrame.join(). Below I have explained using concat() function. For others, please refer to pandas combine two Series to DataFrame
# Convert series to dataframe
courses = pd.Series(["Spark","PySpark","Hadoop"], name='courses')
fees = pd.Series([22000,25000,23000], name='fees')
df=pd.concat([courses,fees],axis=1)
print(df)
# Output:
# courses fees
# 0 Spark 22000
# 1 PySpark 25000
# 2 Hadoop 23000
Convert pandas DataFrame to Series
In this section of the pandas Series Tutorial, I will explain different ways to convert DataFrame to Series. As I explained in the beginning. Given that each column in a DataFrame is essentially a Series, it follows that we can easily extract single or multiple columns from a DataFrame and convert them into Series objects
- You can convert a single-column DataFrame into a Series by extracting that single column.
- To obtain a Series from a specific column in a multi-column DataFrame, simply access that column using its name.
- To convert a single row of a DataFrame into a Series, you can utilize indexing to select the row and obtain it as a Series
Convert a single DataFrame column into a series
To run some examples of converting a single DataFrame column into a series, let’s create a DataFrame. By using DataFrame.squeeze() to convert the DataFrame into a Series:
# Create DataFrame with single column
data = ["Python","PHP","Java"]
df = pd.DataFrame(data, columns = ['Courses'])
my_series = df.squeeze()
print(my_series)
print (type(my_series))
The DataFrame will now get converted into a Series:
# Output:
0 Python
1 PHP
2 Java
Name: Courses, dtype: object
<class 'pandas.core.series.Series'>
Convert the DataFrame column into a series
You can use the .squeeze() method to convert a DataFrame column into a Series.
For example, if we a multiple-column DataFrame
# Create DataFrame with multiple columns
import pandas as pd
data = {'Courses': ['Spark', 'PySpark', 'Python'],
'Duration':['30 days', '40 days', '50 days'],
'Fee':[20000, 25000, 26000]
}
df = pd.DataFrame(data, columns = ['Courses', 'Duration', 'Fee'])
print(df)
print (type(df))
This will convert the Fee column of your DataFrame df into a Series named my_series. If the column contains only one level of data (i.e., it’s not a DataFrame itself), .squeeze() will return it as a Series.
# Pandas DataFrame column to series
my_series= df['Fee'].squeeze()
Convert DataFrame Row into a Series
You can use .iloc[] to access a row by its integer position and then use .squeeze() to convert it into a Series if it has only one element.
# Convert dataframe row to series
my_series = df.iloc[2].squeeze()
print(my_series)
print (type(my_series))
Then, we can get the following series:
# Output:
Courses Python
Duration 50 days
Fee NaN
Name: 2, dtype: object
<class 'pandas.core.series.Series'>
Merge DataFrame and Series?
- Construct a dataframe from the series.
- After that merge with the dataframe.
- Specify the data as the values, multiply them by the length, set the columns to the index and set params for left_index and set the right_index to True.
# Syntax for merge with the DataFrame.
df.merge(pd.DataFrame(data = [s.values] * len(s), columns = s.index), left_index=True, right_index=True)
Pandas Series Attributes:
| T | Return the transpose, which is by definition self. |
| array | The ExtensionArray of the data backing this Series or Index. |
| at | Access a single value for a row/column label pair. |
| attrs | Dictionary of global attributes of this dataset. |
| axes | Return a list of the row axis labels. |
| dtype | Return the dtype object of the underlying data. |
| dtypes | Return the dtype object of the underlying data. |
| flags | Get the properties associated with this pandas object. |
| hasnas | Return if I have any nans; enables various perf speedups. |
| iat | Access a single value for a row/column pair by integer position. |
| iloc | Purely integer-location based indexing for selection by position. |
| index | The index (axis labels) of the Series. |
| is_monotonic | Return boolean if values in the object are monotonic_increasing. |
| is_monotonic_decreasing | Return boolean if values in the object are monotonic_decreasing. |
| is_monotonic_increasing | Alias for is_monotonic. |
| is_unique | Return boolean if values in the object are unique. |
| loc | Access a group of rows and columns by label(s) or a boolean array. |
| name | Return the name of the Series. |
| nbytes | Return the number of bytes in the underlying data. |
| ndim | Number of dimensions of the underlying data, by definition 1. |
| shape | Return a tuple of the shape of the underlying data. |
| size | Return the number of elements in the underlying data. |
| values | Return Series as ndarray or ndarray-like depending on the dtype. |
Pandas Series Methods:
| abs() | Return a Series/DataFrame with absolute numeric value of each element. |
| add(other[, level, fill_value, axis]) | Return Addition of series and other, element-wise (binary operator add). |
| add_prefix(prefix) | Prefix labels with string prefix. |
| add_suffix(suffix) | Suffix labels with string suffix. |
| agg([func, axis]) | Aggregate using one or more operations over the specified axis. |
| aggregate([func, axis]) | Aggregate using one or more operations over the specified axis. |
| align(other[, join, axis, level, copy, …]) | Align two objects on their axes with the specified join method. |
| all([axis, bool_only, skipna, level]) | Return whether all elements are True, potentially over an axis. |
| any([axis, bool_only, skipna, level]) | Return whether any element is True, potentially over an axis. |
| append(to_append[, ignore_index, …]) | Concatenate two or more Series. |
| apply(func[, convert_dtype, args]) | Invoke function on values of Series. |
| argmax([axis, skipna]) | Return int position of the largest value in the Series. |
| argmin([axis, skipna]) | Return int position of the smallest value in the Series. |
| argsort([axis, kind, order]) | Return the integer indices that would sort the Series values. |
| asfreq(freq[, method, how, normalize, …]) | Convert time series to specified frequency. |
| asof(where[, subset]) | Return the last row(s) without any NaNs before where. |
| astype(dtype[, copy, errors]) | Cast a pandas object to a specified dtype . |
| at_time(time[, asof, axis]) | Select values at particular time of day (e.g., 9:30AM). |
| autocorr([lag]) | Compute the lag-N autocorrelation. |
| backfill([axis, inplace, limit, downcast]) | Synonym for DataFrame.fillna() with method=”bfill”. |
| between(left, right[, inclusive]) | Return boolean Series equivalent to left <= series <= right. |
| between_(start_time, end_time[, …]) | Select values between particular times of the day (e.g., 9:00-9:30 AM). |
Continue..
| bfill([axis, inplace, limit, downcast]) | Synonym for DataFrame.fillna() with method=”bfill” . |
| bool() | Return the bool of a single element Series or DataFrame. |
| cat | alias of pandas.core.arrays.categorical.categoricalAccessor |
| clip([lower, upper, axis, inplace]) | Trim values at input threshold(s). |
| combine(other, func[, fill_value]) | Combine the Series with a Series or scalar according to func. |
| combine_first(other) | Update null elements with value in the same location in ‘other’. |
| compare(other[, align_axis, keep_shape, …]) | Compare to another Series and show the differences. |
| convert([infer_objects, …]) | Convert columns to best possible dtypes using dtypes supporting pd.NA. |
| copy([deep]) | Make a copy of this object’s indices and data. |
| corr(other[, method, min_periods]) | Compute correlation with other Series, excluding missing values. |
| count([level]) | Return number of non-NA/null observations in the Series. |
| cov(other[, min_periods, ddof]) | Compute covariance with Series, excluding missing values. |
| cummax([axis, skipna]) | Return cumulative maximum over a DataFrame or Series axis. |
| cummin([axis, skipna]) | Return cumulative minimum over a DataFrame or Series axis. |
| cumprod([axis, skipna]) | Return cumulative product over a DataFrame or Series axis. |
| cumsum([axis, skipna]) | Return cumulative sum over a DataFrame or Series axis. |
| describe([percentiles, include, exclude, …]) | Generate descriptive statistics. |
| diff([periods]) | First discrete difference of element. |
| div(other[, level, fill_value, axis]) | Return Floating division of series and other, element-wise (binary operator truediv). |
| divide(other[, level, fill_value, axis]) | Return Floating division of series and other, element-wise (binary operator truediv). |
| divmod(other[, level, fill_value, axis]) | Return Integer division and modulo of series and other, element-wise (binary operator divmod). |
| dot(other) | Compute the dot product between the Series and the columns of other. |
| drop([labels, axis, index, columns, level, …]) | Return Series with specified index labels removed. |
| drop_duplicate([keep, inplace]) | Return Series with duplicate values removed. |
| droplevel(level[, axis]) | Return Series/DataFrame with requested index / column level(s) removed. |
| dropna([axis, inplace, how]) | Return a new Series with missing values removed. |
| dt | alias of pandas.core.indexes.accessors.CombinedDatetimelikeproperties. |
| duplicated([keep]) | Indicate duplicate Series values. |
| eq(other[, level, fill_value, axis]) | Return Equal to of series and other, element-wise (binary operator eq). |
| equals(other) | Test whether two objects contain the same elements. |
| ewm([com, span, halflife, alpha, …]) | Provide exponential weighted (EW) functions. |
| expanding([min_periods, center, axis, method]) | Provide expanding transformations. |
| explode([ignore_index]) | Transform each element of a list-like to a row. |
| factorize([sort, na_sentinel]) | Encode the object as an enumerated type or categorical variable. |
| ffill([axis, inplace, limit, downcast]) | Synonym for DataFrame.fillna()with method=ffill(). |
| fillna([value, method, axis, inplace, …]) | Fill NA/NaN values using the specified method. |
| filter([items, like, regex, axis]) | Subset the dataframe rows or columns according to the specified index labels. |
| first(offset) | Select initial periods of time series data based on a date offset. |
| first_valid_other() | Return index for first non-NA value or None, if no NA value is found. |
Conclusion
In this pandas Series tutorial, we have learned about what is panda series? how to create a Panda Series with different types of inputs, convert Pandas Series to DataFrame, and vice versa with working examples.
References
- https://pandas.pydata.org/docs/reference/api/pandas.Series.html
- https://www.w3schools.com/python/pandas/pandas_series.asp
- https://towardsdatascience.com/a-practical-introduction-to-pandas-series-9915521cdc69