将 2 个列表和一个字符串转换为字典

Question

P.S: Thank you everybody ,esp Matthias Fripp . Just reviewed  the question You are right I made mistake : String is value not the key 
num=[1,2,3,4,5,6]
pow=[1,4,9,16,25,36]
s= ":subtraction"    
dic={1:1 ,0:s , 2:4,2:s, 3:9,6:s, 4:16,12:s.......}

There is easy way to convert two list to dictionary :

newdic=dict(zip(list1,list2))

but for this problem no clue even with comprehension:

print({num[i]:pow[i] for i in range(len(num))})

Answer 1

In principle, this would do what you want:

nums = [(n, p) for (n, p) in zip(num, pow)]
diffs = [('subtraction', p-n) for (n, p) in zip(num, pow)]
items = nums + diffs
dic = dict(items)

However, a dictionary cannot have multiple items with the same key, so each of your "subtraction" items will be replaced by the next one added to the dictionary, and you'll only get the last one. So you might prefer to work with the items list directly.

If you need the items list sorted as you've shown, that will take a little more work. Maybe something like this:

items = []
for n, p in zip(num, pow):
    items.append((n, p))
    items.append(('subtraction', p-n))
# the next line will drop most 'subtraction' entries, but on 
# Python 3.7+, it will at least preserve the order (not possible 
# with earlier versions of Python)
dic = dict(items)

Answer 2

As others have said, dict cannot contain duplicate keys. You can make key duplicate with a little bit of tweaking. I used OrderedDict to keep order of inserted keys:

from pprint import pprint
from collections import OrderedDict

num=[1,2,3,4,5,6]
pow=[1,4,9,16,25,36]

pprint(OrderedDict(sum([[[a, b], ['substraction ({}-{}):'.format(a, b), a-b]] for a, b in zip(num, pow)], [])))

Prints:

OrderedDict([(1, 1),
             ('substraction (1-1):', 0),
             (2, 4),
             ('substraction (2-4):', -2),
             (3, 9),
             ('substraction (3-9):', -6),
             (4, 16),
             ('substraction (4-16):', -12),
             (5, 25),
             ('substraction (5-25):', -20),
             (6, 36),
             ('substraction (6-36):', -30)])