Python Prepend a list of dicts

Question

I have this list:

[('1', '1')]

and I want to prepend the list with a dict object to look like:

[('All', 'All'), ('1', '1')]

I'm trying:

myList[:0] = dict({'All': 'All'})

But that gives me:

['All', ('1', '1')]

What am I doing wrong?

Your expected output doesn't include a dictionary.... You want a `(key, value)` tuple of your dict inserted into the list? — roganjosh, Jul 27 '18 at 18:24
`myList[:0] = dict({'All': 'All'}).items()` will do this job. — hygull, Jul 27 '18 at 18:33

score 1 · Answer 1 · answered Jul 27 '18 at 18:25

When you use a dict in as an iterable, you only iterate over its keys. If you instead want to iterate over its key/value pairs, you have to use the dict.items view.

l = [('1', '1')]
d = dict({'All': 'All'})
print([*d.items(), *l])
# [('All', 'All'), ('1', '1')]

The * syntax is available in Python 3.5 and later.

l[:0] = d.items()

also works

score 1 · Accepted Answer · answered Jul 27 '18 at 18:26

Use items() of dictionary to get key, value and prepend them to list:

lst = [('1', '1')]
lst = list({'All': 'All'}.items()) + lst

print(lst)
# [('All', 'All'), ('1', '1')]

Note: {'All': 'All'} is a dictionary itself, so dict({'All': 'All'}) in your code is unnecessary.

score 0 · Answer 3 · answered Jul 27 '18 at 18:28

0

You can also have a look at below.

>>> myList = [('1', '1')]
>>>
>>> myList[:0] = dict({'All': 'All'}).items()
>>> myList
[('All', 'All'), ('1', '1')]
>>>

answered Jul 27 '18 at 18:28

hygull

8,464
2
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score 0 · Answer 4 · answered Jul 27 '18 at 18:31

0

For an answer like [('All', 'All'), ('1', '1')], do:

myList = [('1', '1')]
myList = [('All', 'All')] + myList

For more, reference this.

answered Jul 27 '18 at 18:31

Vinayak Bagaria

162
2
6

score 0 · Answer 5 · answered Aug 02 '18 at 06:29

You can refer the function below for appending any dict as list items to already present list. You just have to send a new dict which you want to append with the old list already present with you.

    def append_dict_to_list(new_dict,old_list):
        list_to_append = list(new_dict.items())
        new_list = list_to_append + old_list 
        return new_list 

    print (append_dict_to_list({'All':'All'},[('1', '1')]))

P.S: If you want the new dict to be appended after the existing list, just change the sequence in code as new_list = old_list + list_to_append

Python Prepend a list of dicts

5 Answers5