How to append all elements of one list to another one? [duplicate]

Question

Probably a simple question but I would like to parse the elements of one list individually to another. For example:

a=[5, 'str1'] b=[8, 'str2', a]

Currently

b=[8, 'str2', [5, 'str1']]

However I would like to be b=[8, 'str2', 5, 'str1']

and doing b=[8, 'str2', *a] doesn't work either.

bruno desthuilliers · Accepted Answer · 2017-08-03 12:10:29Z

41

Use extend()

b.extend(a) [8, 'str2', 5, 'str1']

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answered Aug 3, 2017 at 12:09

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Comments

fredtantini · Accepted Answer · 2017-08-03 12:10:35Z

24

You could use addition:

>>> a=[5, 'str1'] >>> b=[8, 'str2'] + a >>> b [8, 'str2', 5, 'str1']

answered Aug 3, 2017 at 12:10

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This is definitely the nicest option. Thanks

abhinav · Accepted Answer · 2017-08-03 12:12:47Z

The efficient way to do this is with extend() method of list class. It takes an iteratable as an argument and appends its elements into the list.

b.extend(a)

Other approach which creates a new list in the memory is using + operator.

b = b + a

Mohideen bin Mohammed · Accepted Answer · 2017-08-03 12:11:56Z

>>> a [5, 'str1'] >>> b=[8, 'str2'] + a >>> b [8, 'str2', 5, 'str1'] >>>

for extend() you need to define b and a individually...

then b.extend(a) will work

MSeifert · Accepted Answer · 2017-08-03 12:10:21Z

You can use slicing to unpack a list inside another list at an arbitrary position:

>>> a=[5, 'str1'] >>> b=[8, 'str2'] >>> b[2:2] = a # inserts and unpacks `a` at position 2 (the end of b) >>> b [8, 'str2', 5, 'str1']

Similarly you could also insert it at another position:

>>> a=[5, 'str1'] >>> b=[8, 'str2'] >>> b[1:1] = a >>> b [8, 5, 'str1', 'str2']