打印字典中的元素时，打印命令中的 0 索引是什么？

Question

I've tried this piece of code but I don't understand why we use the 0 index in {0[a]}.

Day={'a':'Saturday','b':'Sunday','c':'Monday',
      'd':'Tuesday','e':'Wednesday','f':'Thursday','g':'Friday'}

print('the first days is {0[a]} , second days is {0[b]}'.format(Day))

Answer 1

0 refers to the first argument passed to the format(...) function. 1 is the second, and so on.

Alternatively, you can pass name arguments to format , and use their names in the string.

Answer 2

0 is referring to the first argument of the str.format method.
Your print is thus equivalent to

print('the first days is {0} , second days is {1}'.format(Day['a'], Day['b']))

or

print(f"the first days is {Day['a']} , second days is {Day['b']}")

Answer 3

0 is not for indexing the dictionary, it is for getting the first item in the .format(..) parenthesis.

Example:

>>> '{0} {1}'.format('Hello', 'World')
'Hello World'
>>>