计算字符串中子字符串出现的次数 - Count number of occurrences of a substring in a string

问题：

How can I count the number of times a given substring is present within a string in Python?如何计算给定子字符串出现在 Python 字符串中的次数？

For example:例如：

>>> 'foo bar foo'.numberOfOccurrences('foo')
2

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解决方案：

参考一： https://stackoom.com/question/bLGr
参考二： Count number of occurrences of a substring in a string