Pitfalls to pay attention to when deleting elements from python list

The following is a sharing of pitfalls that you should pay attention to when deleting elements from a python list. It has a good reference value and I hope it will be helpful to everyone. Let’s take a look together

Let’s directly give the code whose output is different from expected

In[28]: a = [1,2,3,4,5,6]
In[29]: for i in a:
 ...:  a.remove(i)
 ...:  
In[30]: a
Out[30]: [2, 4, 6]

In the above for loop, assuming we delete the value of index=2, the original index=3 and subsequent values ​​will be filled forward, so the original index=3 variable is skipped in the loop

Similarly, when using the list.pop() function to delete specified elements, the above situation will also occur, such as:

In[33]: a = [1,2,3,4,5,6]
In[34]: for index, value in enumerate(a):
 ...:  a.pop(index)
 ...:  
In[35]: a
Out[35]: [2, 4, 6]

If we want to delete elements in the list in a loop, the simpler methods available are: use a temporary list to save the elements to be deleted, and loop the temporary list in a for loop to delete elements in the old list; or directly Overwrite the original list with the remaining element list

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