How to use string.format with nested dict

Question

I have a nested dict:

KEYS1 = ("A", "B", "C")
KEYS2 = ("X", "Y", "Z")

d = dict.fromkeys(KEYS1, dict.fromkeys(KEYS2, 0))

I'd now like to embed its values in a string using format, something like

print("d['A']['X']={A,X:d}".format(**d))

to output:

d['A']['X']=0

That does not work. Any suggestions on how to do this correctly?

Answer 1

KEYS1 = ("A", "B", "C")
KEYS2 = ("X", "Y", "Z")

d = dict.fromkeys(KEYS1, dict.fromkeys(KEYS2, 0))

print("d['A']['X']={A[X]}".format(**d))

Output:

d['A']['X']=0

From python 3.6 you will be able to access the dict in the string use Literal string interpolation:

In [23]: print(f"d['A']['X']={d['A']['X']}")
d['A']['X']=0

Answer 2

You can take advantage of str.format's ability to do subscripting on the arguments you provide.

KEYS1 = ("A", "B", "C")
KEYS2 = ("X", "Y", "Z")

d = dict.fromkeys(KEYS1, dict.fromkeys(KEYS2, 0))

print("d['A']['X']={[A][X]}".format(d))

This is really similar to Padraic Cunningham's answer, which is also a good and correct way to do it (which is why I +1'd it). The difference is that in his answer, the part of the string {A[X]} means that the .format method is looking for a keyword argument, which gets provided by unpacking the dict d.

In my method, it is expecting a positional argument, which must be a dict with a key 'A', which must also be a dict with the key 'X'