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How to Use the Python count() Function

Python Count() Function

Hi, Folks! In this article, we will be focusing on Python count() method with Strings and Lists.


1. Python count() function with Strings

Python String has got an in-built function – string.count() method to count the occurrence of a character or a substring in the particular input string.

The string.count() method accepts a character or a substring as an argument and returns the number of times the input substring happens to appear in the string.

Syntax:

string.count(string, start_index,end_index)
  • substring(mandatory): The string whose occurrence of presence needs to be counted in the input string.
  • start_index(optional): The index from where the search for the substring starts.
  • end_index(optional): The index where the search for the substring needs to stop.

Example:

inp_str = "JournalDev -- AskPython @ JournalDev"
str_cnt = inp_str.count("JournalDev")
print(str_cnt)

Output:

2

Example 2:

inp_str = "Python Java Python Kotlin"
str_cnt = inp_str.count("Python", 0 , 6)
print(str_cnt)

In the above example, we have passed ‘Python‘ as a substring to be searched and to count for the presence between index 0 – index 6.

Output:

1

Example 3:

inp_str = "Python Java Python Kotlin"
str_len=len(inp_str)
str_cnt = inp_str.count("Python", 5 , str_len )
print(str_cnt)

Here, we search the substring – ‘Python’ and count its occurrence between index 5 to the end of the string that is why we have passed the length of the string as the end_index argument.

Output:

1

Python String count() method: TypeError

Python string.count() accepts only a single substring as an argument. If we try to pass multiple substrings as arguments, it raises the TypeError exception.

Example:

inp_str = "Python Java Python Kotlin"
str_cnt = inp_str.count('Python', 'Java')
print(str_cnt)

Output:

TypeError                                 Traceback (most recent call last)
<ipython-input-40-6084d1350592> in <module>
      1 inp_str = "Python Java Python Kotlin"
----> 2 str_cnt = inp_str.count('Python', 'Java')
      3 print(str_cnt)

TypeError: slice indices must be integers or None or have an __index__ method


2. Python List count() function

Python list has got a list.count() method to count the occurrence of particular elements in a list.

The list.count() method counts the occurrence of a particular value/ data item present in the input list.

Syntax:

list.count(value)

Example 1:

inp_lst = ['Apple','Banana','Apple','Grapes','Jackfruit','Apple']

lst_cnt = inp_lst.count('Apple')
print(lst_cnt)

Output:

3

Example 2:

inp_lst = [ ['Rat','Cat'], ['Heat','Beat'], ['Rat','Cat'] ]

lst_cnt = inp_lst.count(['Rat','Cat'])
print(lst_cnt)

In the above example, we basically count the occurrence of a nested list [‘Rat’, ‘Cat’] inside the list.

Output:

2

Python count() function at a glance!

  • Python string.count() function is used to count for the occurrence of the input substring in the particular String.
  • The string.count() method raises an TypeError exception, if we try to pass more than one substring as an argument.
  • The list.count() function checks for the number of times a particular element occurs in a particular list.

Conclusion

Thus, in this article, we have understood the working of in-built Python count function with Strings and Lists.


References