Structured Programming in Python - SourceForge

That is, word2 is a copy of word1, so when we overwrite word1 with a new string ’Python’ in line a, the value of word2 is not affected. However, assignment statements do not always involve making copies in this way. An important subtlety of Python is that the “value” of a structured object (such as a list) is actually a reference to the ... ................
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