Python Counter.update() Method
Last Updated :
03 Apr, 2024
Python's Counter is a subclass of the dict class and provides a convenient way to keep track of the frequency of elements in an iterable. The Counter.update() method is particularly useful for updating the counts of elements in a Counter object based on another iterable or another Counter object. In this article, we will understand about the Counter.update() method.
What is Python Counter.update() Method?
The Counter.update() method updates the counts of elements in a Counter object based on the elements provided in an iterable or another Counter object. It takes an iterable or a mapping (such as another Counter) as its argument and increments the counts of elements accordingly.
Syntax of Counter.update() Function
Counter.update(iterable_or_mapping)
Python Counter.update() Method Examples
Below are some of the examples by which we can understand about Counter.update() method in Python:
Updating Counts from an Iterable
In this example, the counts of 'apple' and 'banana' are updated based on the elements in the fruits list.
Python3
from collections import Counter
# Initial Counter
fruit_counter = Counter({'apple': 2, 'banana': 1})
# Update counts from an iterable
fruits = ['apple', 'banana', 'apple', 'orange', 'apple']
fruit_counter.update(fruits)
print("Updated Counter:", fruit_counter)
OutputUpdated Counter: Counter({'apple': 5, 'banana': 2, 'orange': 1})
Combining Counters Using Counter.update() Function
In this example, the counts of elements in counter1 are updated based on the counts in counter2.
Python3
from collections import Counter
# Initial Counters
counter1 = Counter({'a': 3, 'b': 2})
counter2 = Counter({'a': 1, 'b': 4, 'c': 2})
# Combine counters
counter1.update(counter2)
print("Combined Counter:", counter1)
OutputCombined Counter: Counter({'b': 6, 'a': 4, 'c': 2})
Updating Counts with Generator Expression
In this example, we use a generator expression to convert each word to lowercase before updating the counts in the word_counter.
Python3
from collections import Counter
# Initial Counter
word_counter = Counter({'apple': 2, 'banana': 1})
# Update counts from a generator expression
words = ('apple', 'banana', 'apple', 'orange', 'apple')
word_counter.update((word.lower() for word in words))
print("Updated Counter:", word_counter)
OutputUpdated Counter: Counter({'apple': 5, 'banana': 2, 'orange': 1})
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