Pandas Series.sort_values() With Examples

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  • Post last modified:March 27, 2024
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Pandas Series.sort_values() function is used to sort values on Series object. It sorts the series in ascending order or descending order, by default it does in ascending order. You can specify your preference using the ascending parameter which is True by default. In this article, you can find out how to sort values in pandas series with multiple examples.

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Key Points –

  • Series.sort_values() is a Pandas method that allows you to sort the values of a Pandas Series in ascending or descending order.
  • Series.sort_values() supports the use of a custom sorting criteria through the key parameter. This allows you to define a function that determines the sorting order based on specific conditions or transformations of the values.
  • By default, the method sorts the Series in ascending order. This means that the smallest values will be at the beginning of the Series.
  • The method has an optional parameter inplace that, when set to True, modifies the original Series in place. Otherwise, it returns a new sorted Series without modifying the original.
  • The method provides options to control the treatment of NaN (Not a Number) values during sorting. You can specify whether NaN values should be placed at the beginning or end of the sorted Series.
  • Apart from sorting by values, the method also allows sorting based on the index of the Series, providing flexibility in arranging data based on both values and index.

1. Quick Examples of Sort Pandas Series

If you are in hurry below are some quick examples of how to sort values of DataFrame by using Series.sort_values().


# Quick examples of sort series

# Sort pandas Series in an ascending order
sortedSeries = mySeries.sort_values()
sortedSeries = mySeries.sort_values(ascending=True)

# Sort pandas Series in a descending order
sortedSeries = mySeries.sort_values(ascending=False)

# Sort inplace
mySeries.sort_values(ascending=False, inplace=True)

# Sort Series Contains Numeric Values
import pandas as pd
mySeries = pd.Series([25000,30000,23000,15000,80000])
mySeries.sort_values(ascending=True)

# Sort Series which contains NAN Values
# Keeping NaN as first. By default it puts at last
sortedSeries = Series.sort_values(ascending=True, na_position='first')
print(sortedSeries)

2. Syntax of Series.sort_values()

Following is the syntax of the Series.sort_values(). This takes params axis, ascending, inplace, kind and na_position and returns a sorted Series object. With inplace=True param it returns None.


# Syntax of Series.sort_values()
Series.sort_values(axis=0, ascending=True, inplace=False, kind='quicksort', na_position='last', ignore_index=False, key=None)
  • axis – The axis along which the sorting will be done (0 for rows, 1 for columns).
  • ascending – A boolean or list of booleans indicating whether to sort in ascending order (default) or descending order.
  • inplace – A boolean indicating whether to perform the sorting in-place or return a new sorted Series.
  • kind – The sorting algorithm to be used (‘quicksort’, ‘mergesort’, ‘heapsort’, or ‘stable’).
  • na_position – Specifies the placement of NaN values during sorting (‘first’ or ‘last’).
  • ignore_index – If True, the resulting Series will have a new index.
  • key – A function that will be used to extract a comparable key from each element for custom sorting.

Now, Let’s create a pandas series.


# Create a pandas series.
import pandas as pd
series = pd.Series(['JAVA','PySpark','Spark','Hadoop'])
print(series)

Yields below output.


# Output:
0      Spark
1    PySpark
2       JAVA
3     Hadoop
dtype: object

3. Sort the Series in Ascending Order

By default, the pandas series sort_values() function sorts the series in ascending order. You can also use ascending=True param to explicitly specify to sort in ascending order. Also, if you have any NaN values in the Series, it sort by placing all NaN values at the end. You can change this behavior by using na_position param.


# Sort the series in ascending order.
sortedseries = series.sort_values()
(or)
sortedseries = series.sort_values(ascending=True)
print(sortedseries)

Yields below output.


# Output:
3     Hadoop
0       JAVA
1    PySpark
2      Spark
dtype: object

Note that the sort_values() function returns a sorted copy of the original series. To modify the original series in-place, pass inplace=True to the function.


# Sort the series in ascending order.
series.sort_values(inplace=True)
(or)
series.sort_values(ascending=True,inplace=True)

4. Sort Series in Descending Order

To sort a Pandas Series in descending order, you can use the Series.sort_values() method with the ascending parameter set to False.


# Sort series in descending order.
sortedseries = series.sort_values(ascending=False)
print(sortedseries)

In this example, ascending=False is used to sort the Series in descending order. The resulting sorted_series_desc will have the values sorted from the largest to the smallest. This example yields the below output.


# Output:
2      Spark
1    PySpark
0       JAVA
3     Hadoop
dtype: object

5. Sort Series that Contains Numeric Values

Let’s now see how to sort a Series that includes numeric values. Now, create the following Pandas Series that contains only numeric values.


# Sort Series Contains Numeric Values.
import pandas as pd
series = pd.Series([25000,30000,23000,15000,80000])
print(series)

Now, to sort a Pandas Series that contains numeric values, you can use the Series.sort_values() method. For instance, the sort_values() method is used to sort the series. The default behavior is to sort in ascending order, and you can set ascending=False to sort in descending order.


# Sort the Series in an ascending order.
sortedSeries = Series.sort_values(ascending=True)
print(sortedSeries)

Yields below output.


# Output:
3    15000
2    23000
0    25000
1    30000
4    80000
dtype: int64

6. Sort Series Which Contains NaN Values

Now, let’s create a Series with NaN values using the Numpy library and then place the NaN values at the last while the other values will be sorted in ascending order. By default, it places all NaN values at the last.


import pandas as pd
import numpy as np
# Create Series with NaN values
Series = pd.Series([25000,np.NaN,23000,15000,80000])
print(Series)

# Sort Series which contains NAN Values.
sortedSeries = Series.sort_values(ascending=True)
print(sortedSeries)

Yields below output.


# Output:
3    15000.0
2    23000.0
0    25000.0
4    80000.0
1        NaN
dtype: float64

Similarly, you can use the na_position parameter to control the placement of NaN values during sorting. If you want to place NaN values at the beginning when sorting in descending order, you can set na_position='first'.


# Sort the Series by keeping NaN as first
sortedSeries = Series.sort_values(ascending=True, na_position='first')
print(sortedSeries)

In the above example, na_position='first' ensures that NaN values are placed at the beginning of the sorted Series when sorting in descending order. This example yields the below output.


# Output:
1        NaN
3    15000.0
2    23000.0
0    25000.0
4    80000.0
dtype: float64

7. Complete Examples to Sort Series Contains NAN Values


# Sort pandas Series in an ascending order:
sortedSeries = mySeries.sort_values()
sortedSeries = mySeries.sort_values(ascending=True)

# Sort pandas Series in a descending order.
sortedSeries = mySeries.sort_values(ascending=False)

# Sort inplace
mySeries.sort_values(ascending=False, inplace=True)

# Sort Series Contains Numeric Values.
import pandas as pd
mySeries = pd.Series([25000,30000,23000,15000,80000])
mySeries.sort_values(ascending=True)

# Sort Series which contains NAN Values.
# Keeping NaN as first. By default it puts at last
sortedSeries = Series.sort_values(ascending=True, na_position='first')
print(sortedSeries)

Frequently Asked Questions on Pandas Series.sort_values() 

What is the purpose of Series.sort_values() in Pandas?

The Series.sort_values() method in Pandas is used to sort the values of a Series in either ascending or descending order. It allows for flexible data manipulation and exploration by arranging values according to user-specified criteria.

How does Series.sort_values() handle ties in the data?

By default, Series.sort_values() performs stable sorting. In case of ties (equal values), the original order of those tied elements is preserved in the result. This ensures that the sorting operation is deterministic and reproducible.

Does Series.sort_values() work with non-numeric data?

Series.sort_values() can be used with both numeric and non-numeric data. It is a versatile method that can handle sorting based on any comparable data type, including strings, dates, or custom objects, depending on the data contained in the Series.

Can I sort a Pandas Series in descending order without modifying the original Series?

Series.sort_values() provides the inplace parameter. If inplace is set to False (the default), a new sorted Series is returned, leaving the original Series unchanged. Setting inplace=True modifies the original Series in place.

What does the na_position parameter control in Series.sort_values()?

The na_position parameter specifies the placement of NaN (Not a Number) values during sorting. It can be set to ‘first’ to place NaN values at the beginning of the sorted Series or ‘last’ to place them at the end. The default is ‘last’.

Can I customize the sorting criteria using Series.sort_values()?

The method provides the key parameter, allowing you to specify a custom sorting function. This function is applied to each element in the Series, and the values are sorted based on the results of this function rather than the raw values themselves.

Conclusion

In this article, you have learned how to sort values in pandas series by using Series.sort_values() It sorts the series in ascending order or descending order. By default, it does in ascending order and places all NaN values at the last.

References

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