Overview:
- The count() function returns the number of elements present in a pandas.Series instance.The NA/null/None values are not included in the count value.
- The nunique() function returns the number of unique elements present in the pandas.Series.
- The function Series.unique() returns the unique elements excluding the duplicate values present in a pandas.Series. Determining uniqueness of the elements is done through a hash table.
Example - Counting elements of a pandas.series:
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# Example Python program to count the number of # elements present in a pandas.Series instance import pandas as pds
cities = ["London", "Paris", "Madrid", "NewYork", "Chicago", "San Francisco"];
# Create a pandas.Series instance series = pds.Series(cities); print("Contents of the pandas.series:"); print(cities);
print("Number of elements present in the pandas.series:"); print(series.count()); |
Output:
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Contents of the pandas.series: ['London', 'Paris', 'Madrid', 'NewYork', 'Chicago', 'San Francisco'] Number of elements present in the pandas.series: 6 |
Example-Count and get the unique elements present in a pandas.series:
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# Example Python program to get unique elements present in a pandas.Series import pandas as pds
# Create a pandas.Series instance numbers = pds.Series([1,2,3,5,7,3,5,7,3,5,7]); print("Contents of the Series:"); print(numbers);
print("Number of Unique elements present in the Series:"); print(numbers.nunique());
print("Unique elements of the Series:"); print(numbers.unique()); |
Output:
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Contents of the Series: 0 1 1 2 2 3 3 5 4 7 5 3 6 5 7 7 8 3 9 5 10 7 dtype: int64 Number of Unique elements present in the Series: 5 Unique elements of the Series: [1 2 3 5 7]
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Example- Get the unique class objects present in a pandas.series:
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# Example Python program to get unique elements present in a pandas.Series import pandas as pds
class X: def __init__(self, name): self.name = name;
def __str__(self): return self.name;
# Unique elements x1 = X("x1"); x2 = X("x2"); x3 = X("x3");
# Copy x4 = x1;
# Copy is not returned as identity of x1 and x4 are same xSeries = pds.Series([x1, x2, x3, x4]); uniques = xSeries.unique();
print("Unique objects:"); print(uniques);
# First and fourth elements have indeed different identities xDashSeries = pds.Series([X("One"), X("Two"), X("Three"), X("One")]); uniques = xDashSeries.unique();
print("Unique objects:") print(uniques); |
Output:
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Unique objects: [<__main__.X object at 0x1100db438> <__main__.X object at 0x1100db470> <__main__.X object at 0x1100db4a8>] Unique objects: [<__main__.X object at 0x11c0a8da0> <__main__.X object at 0x11d4fe0b8> <__main__.X object at 0x11d4fe048> <__main__.X object at 0x11d52a940>] |