Функция count в питон

Как использовать метод count() при работе со списками, кортежами и строками в Python

count() является методом, который можно применять к спискам, кортежам и строкам в Python. Он используется для подсчета количества вхождений указанного элемента в последовательности.

Синтаксис

Синтаксис метода count() выглядит так:

Здесь sequence — это список, кортеж или строка, в которых нужно произвести поиск, а element — это элемент, количество вхождений которого нужно подсчитать.

Примеры использования

Давайте рассмотрим несколько примеров использования метода count() для каждого из этих типов данных.

Списки

Использование метода count() в списках:

my_list = [1, 2, 3, 4, 4, 5, 4] count_of_fours = my_list.count(4) print(count_of_fours) #3

Результат выполнения этого кода будет равен «3», потому что в списке три элемента со значением «4».

Кортежи

Использование метода count() в кортежах:

my_tuple = (1, 2, 3, 4, 4, 5, 4) count_of_fours = my_tuple.count(4) print(count_of_fours) #3

Этот код также выведет число «3», потому что кортеж содержит те же элементы, что и список в предыдущем примере.

Строки

Использование метода count() в строках:

my_string = "Hello, World!" count_of_l = my_string.count('l') print(count_of_l) #3

Этот код выведет число «3», потому что символ l встречается в строке три раза.

Метод count() также можно использовать для поиска подстрок в строках:

my_string = "Hello, World!" count_of_lo = my_string.count('lo') print(count_of_lo) #1

Этот код выведет число «1», потому что подстрока lo встречается в строке только один раз.

Кроме того, метод count() возвращает ноль, если элемент не найден в последовательности:

my_list = [1, 2, 3, 4, 4, 5, 4] count_of_nines = my_list.count(9) print(count_of_nines) #0

Этот код выведет число «0», потому что элемент «9» не найден в списке.

Наконец, следует отметить, что метод count() не изменяет исходную последовательность, а только возвращает количество вхождений указанного элемента.

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Источник

Count in Python

The count() function of the python is used to count the frequency of the character or a substring in a string. It simply gives the count of occurrences as a return value.

Syntax of count() Function in Python

Python Count() function has following syntax:

Parameters of count() Fucntion in Python

Three parameters are accepted by the count() function of python while using strings:

• substring/character : Which is to be searched in the string.
• start (optional) : The value which is stated as the start position. It is inclusive, which means substring/character at this position is also included in the count. If we leave this parameter empty, then start is considered as 0 th position by default.
• end (optional) : The value stated as the end position. It is exclusive, which means substring/character at this position is excluded from the count. If we leave this parameter empty, then the end is considered the last index of the string by default.

Return Value of count() Fucntion in Python

Return Type: integer

It returns the number of occurrences of substring/character in a string.

Example of count() Fucntion in Python

Let’s use count() function on strings to find the occurrence of any character.

Explanation

• We created a string and stored it into a variable.
• Then, we calculated the occurrence of the character ‘e’ in the string and stored it in the variable.
• Finally, we printed that variable and got the occurrence of ‘e’ in the string.

What is the count() Function in Python?

Let’s say you have a very long binary string(a string that only consists of 0’s and 1’s), and you have a tedious job of counting the number of occurrences of ‘1’ in that string. Have you ever wondered how you would solve this long task within a single second? If you use Python Count() function to find the number of occurrences of ‘1’ in that string, you get desired output within milliseconds.

The python count() function is an inbuilt function of python which is used to count the number of occurrences of a character or substring in the string. Count function is case-sensitive it means that ‘a’ & ‘A’ are not treated as the same.

Application of count() Function in Python

• Count function can find the white spaces in a given string.
• Count function can determine the frequency of any character in a given string.
• Count function can also be used to find out the count of a given word from a string.

Python count() function is used with both string and array/list. When used with array and list, the count() function have a different syntax and parameter but the same return value.

More Examples

Example 1: Using Count Method with a Substring.

Let’s use count() function on strings to find the occurrence of any of its substring(more than one character) in that string.

Explanation

• We created a string and stored it into a variable.
• Then, we calculated the occurrence of substring ‘abcd’ from the string and stored it in the variable.
• Finally, we printed that variable and got the occurrence of ‘abcd’ in the string as an output.

Example 2: Count method with Character in a Given Binary String

Let’s use count() on strings to find the occurrence of any of its character in that binary string.

Explanation

• We created a string and stored it into a variable.
• Then, we calculated the occurrence of character ‘0’ from the string and stored it in the variable.
• Finally, we printed that variable and got the occurrence of ‘0’ in the string as an output.

Example 3: Count method with Substring in a Given Binary String

Let’s use count() on strings to find the occurrence of any of its substring(more than one character) in that string.

Explanation

• We created a string and stored it into a variable.
• Then, we calculated the occurrence of substring ’01’ from string and stored it in the variable.
• Finally, we printed that variable and got the occurrence of ’01’ in the string as an output.

Example 4: Using Start Position Parameters

Let’s use count() on strings to find the occurrence of any of its substring(more than one character) in that string by passing only one optional parameter start , for specifying the start position for finding the substring.

Explanation

• We created a string and stored it into a variable.
• Then, we calculated the occurrence of substring ‘ab’ in a string starting from position 11(inclusive) till the end of the string and stored it in the variable.
• Finally, we printed that variable and got the occurrence of ‘ab’ in the string as an output.

Example 5: Using End Position Parameters

Let’s use count() function on strings to find the occurrence of any of its substring(more than one character) in that string by passing only one optional parameter end for specifying the end position till there we have to find the substring.

While we are only sending a single optional parameter end in count() function. We have to use start parameter as None to specify that we have to start counting from the start of the string.

Explanation

• We created a string and stored it into a variable.
• Then, we calculated the occurrence of substring ‘ab’ in the string from starting of the string till position 15(exclusive) and stored it in the variable.
• Finally, we printed that variable and got the occurrence of ‘ab’ in the string as an output.

Example 6: Using both Optional Parameters

Let’s use count() on strings to find the occurrence of any of its characters in that string by passing some additional optional parameters start & end as discussed earlier.

Explanation

• We created a string and stored it into a variable.
• Then, we calculated the occurrence of character ‘e’ in the string from the position between 3(inclusive) and 14(exclusive) and then stored it in the variable.
• Finally, we printed that variable and got the occurrence of ‘e’ in the string as an output.

Conclusion

• First of all, we understood what count() in python and the basic use of the count function, and we discussed the syntax, parameters, and the return value of the count function.
• The function returns the number of occurrences of provided character/substring in the string.
• We can provide the start and end position of the string to count the occurrences in only a specified portion of the string.

Read More:

Источник

Python List count() Method

Return the number of times the value «cherry» appears in the fruits list:

fruits = [‘apple’, ‘banana’, ‘cherry’]

Definition and Usage

The count() method returns the number of elements with the specified value.

Syntax

Parameter Values

More Examples

Example

Return the number of times the value 9 appears int the list:

points = [1, 4, 2, 9, 7, 8, 9, 3, 1]

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