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Counting number of times a substring appears in a string

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One method is available for counting the number of occurrences of a sub-string in another string, str.count.

str.count(sub[, start[, end]])

str.count returns an int indicating the number of non-overlapping occurrences of the sub-string sub in another string. The optional arguments start and end indicate the beginning and the end in which the search will take place. By default start = 0 and end = len(str) meaning the whole string will be searched: 

>>> s = "She sells seashells by the seashore."
>>> s.count("sh")
2
>>> s.count("se")
3
>>> s.count("sea")
2
>>> s.count("seashells")
1

By specifying a different value for start, end we can get a more localized search and count, for example, if start is equal to 13 the call to: 

>>> s.count("sea", start)
1

is equivalent to: 

>>> t = s[start:]
>>> t.count("sea")
1
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String Methods:
* String Methods
* Changing the capitalization of a string
* str.translate Translating characters in a string
* str.format and f-strings Format values into a string
* String modules useful constants
* Replace all occurrences of one substring with another substring
* Reversing a string
* Testing what a string is composed of
* Split a string based on a delimiter into a list of strings
* Stripping unwanted leading/trailing characters from a string
* String Contains
* Join a list of strings into one string
* Counting number of times a substring appears in a string
* Case insensitive string comparisons
* Test the starting and ending characters of a string
* Justify strings
* Conversion between str or bytes data and unicode characters
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