2.6: String operations
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In general, you can’t perform mathematical operations on strings, even if the strings look like numbers, so the following are illegal:
'chinese'-'food' 'eggs'/'easy' 'third'*'a charm'
But there are two exceptions, + and *.
The + operator performs string concatenation, which means it joins the strings by linking them end-to-end. For example:
>>> first = 'throat' >>> second = 'warbler' >>> first + second throatwarbler
The * operator also works on strings; it performs repetition. For example,
'SpamSpamSpam'. If one of the values is a string, the other has to be an integer.
This use of + and * makes sense by analogy with addition and multiplication. Just as
4*3 is equivalent to
4+4+4, we expect
'Spam'*3 to be the same as
'Spam'+'Spam'+'Spam', and it is. On the other hand, there is a significant way in which string concatenation and repetition are different from integer addition and multiplication. Can you think of a property that addition has that string concatenation does not?