# 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, 'Spam'*3 is '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?

This page titled 2.6: String operations is shared under a CC BY-NC 3.0 license and was authored, remixed, and/or curated by Allen B. Downey (Green Tea Press) .