How to insert the contents of one list into another
Question:
I am trying to combine the contents of two lists, in order to later perform processing on the entire data set. I initially looked at the built in insert function, but it inserts as a list, rather than the contents of the list.
I can slice and append the lists, but is there a cleaner / more Pythonic way of doing what I want than this:
array = ['the', 'fox', 'jumps', 'over', 'the', 'lazy', 'dog']
addition = ['quick', 'brown']
array = array[:1] + addition + array[1:]
Answers:
You can do the following using the slice syntax on the left hand side of an assignment:
>>> array = ['the', 'fox', 'jumped', 'over', 'the', 'lazy', 'dog']
>>> array[1:1] = ['quick', 'brown']
>>> array
['the', 'quick', 'brown', 'fox', 'jumped', 'over', 'the', 'lazy', 'dog']
That’s about as Pythonic as it gets!
The extend method of list object does this, but at the end of the original list.
addition.extend(array)
insert(i,j), where i is the index and j is what you want to insert, does not add as a list. Instead it adds as a list item:
array = ['the', 'fox', 'jumps', 'over', 'the', 'lazy', 'dog']
array.insert(1,'brown')
The new array would be:
array = ['the', 'brown', 'fox', 'jumps', 'over', 'the', 'lazy', 'dog']
Leveraging the splat operator / list unpacking for lists you can do it using
array = ['the', 'fox', 'jumps', 'over', 'the', 'lazy', 'dog']
addition = ['quick', 'brown']
# like this
array2 = ['the', *addition, 'fox', 'jumps', 'over', 'the', 'lazy', 'dog']
# or like this
array = [ *array[:1], *addition, *array[1:]]
print(array)
print(array2)
to get
['the', 'quick', 'brown', 'fox', 'jumped', 'over', 'the', 'lazy', 'dog']
The operator got introduces with PEP 448: Additional Unpacking Generalizations.
I am trying to combine the contents of two lists, in order to later perform processing on the entire data set. I initially looked at the built in insert function, but it inserts as a list, rather than the contents of the list.
I can slice and append the lists, but is there a cleaner / more Pythonic way of doing what I want than this:
array = ['the', 'fox', 'jumps', 'over', 'the', 'lazy', 'dog']
addition = ['quick', 'brown']
array = array[:1] + addition + array[1:]
You can do the following using the slice syntax on the left hand side of an assignment:
>>> array = ['the', 'fox', 'jumped', 'over', 'the', 'lazy', 'dog']
>>> array[1:1] = ['quick', 'brown']
>>> array
['the', 'quick', 'brown', 'fox', 'jumped', 'over', 'the', 'lazy', 'dog']
That’s about as Pythonic as it gets!
The extend method of list object does this, but at the end of the original list.
addition.extend(array)
insert(i,j), where i is the index and j is what you want to insert, does not add as a list. Instead it adds as a list item:
array = ['the', 'fox', 'jumps', 'over', 'the', 'lazy', 'dog']
array.insert(1,'brown')
The new array would be:
array = ['the', 'brown', 'fox', 'jumps', 'over', 'the', 'lazy', 'dog']
Leveraging the splat operator / list unpacking for lists you can do it using
array = ['the', 'fox', 'jumps', 'over', 'the', 'lazy', 'dog']
addition = ['quick', 'brown']
# like this
array2 = ['the', *addition, 'fox', 'jumps', 'over', 'the', 'lazy', 'dog']
# or like this
array = [ *array[:1], *addition, *array[1:]]
print(array)
print(array2)
to get
['the', 'quick', 'brown', 'fox', 'jumped', 'over', 'the', 'lazy', 'dog']
The operator got introduces with PEP 448: Additional Unpacking Generalizations.