Appending to a List

L = ['abc', 'ADB', 'aBe']

L[开发者_开发问答len(L):]=['a1', 'a2'] # append items at the end...
L[-1:]=['a3', 'a4'] # append more items at the end...

... works, but 'a2' is missing in the output:

['abc', 'ADB', 'aBe', 'append', 'a1', 'a3', 'a4']

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I think that the -1 is pointing at the last element of the list, which gets overwritten by 'a3'. As described here, you can do a

list.extend(['a3', 'a4'])

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Use L.append (for a single element) or L.extend (for a sequence) -- there's absolutely no call for playing fancy "assign-to-slice" tricks (especially if you don't master them!-). The slice [-1:] means "last element included onwards" -- so, by assigning to that slice, you're obviously "overwriting" the last element!

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What is wrong with:

L.append('a1')

or

L += ['a1', 'a2']

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to append items to a list, you can use +

L + ["a1","a2"]

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Your 3rd assignment is overwriting the 'a2' value.

Perhaps you should be using a more straightforward method:

L = ['abc', 'ADB', 'aBe']
L += ['a1', 'a2']
L += ['a3', 'a4']
Etc.

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Use the extend method

L = ['abc', 'ADB', 'aBe']
L.extend(['a1', 'a2'])
L.extend(['a3', 'a4'])