Quote:
How does list1 have 'a' in its output
This have to do with how Python internally deals with pointers.
When you store a list in a variable, the list is not copied, instead a pointer to actual list is stored in variable, it is both memory efficient and fast.
What is counter intuitive to me is that
list=[]
do not create a new list the second time, but reuse the same as first time.
Have look at documentation for details about lists and pointers.
Use the debugger to see exactly what is going on.
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Your code do not behave the way you expect, or you don't understand why !
There is an almost universal solution: Run your code on debugger step by step, inspect variables.
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't know what your code is supposed to do, it don't find bugs, it just help you to by showing you what is going on. When the code don't do what is expected, you are close to a bug.
To see what your code is doing: Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.
Debugger - Wikipedia, the free encyclopedia[
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27.3. pdb — The Python Debugger — Python 3.6.1 documentation[
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Debugging in Python | Python Conquers The Universe[
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pdb – Interactive Debugger - Python Module of the Week[
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The debugger is here to only show you what your code is doing and your task is to compare with what it should do.