A few things to note about Python

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1. The value of the mutable type is not used as the default value for the function parameter

2. Be careful + =

A = range (Ten) b = Range (5) A_orig = a A + = b print a print A_orig # A_orig The value is changed during the above process.
A = range (Ten) b = Range (5) A_orig = a = a + b print a print A_orig # A_orig or the original value, unchanged.

========= Performance =======

1, RANGE returns the iteration object returned by List,xrange, so xrange saves memory

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3, more efficient than their for

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A few things to note about Python