how to print the list value of the nested dictionary-CodePudding

I have created the following dictionary:

Book_list={
 'Fiction': {1001: ['Pride and Prejudice', 'available'],
             1002: ['Fahrenheit 451', 'available']},
 'Horror': {2001: ['House of leaves', 'available'],
            2002: ['The Shinking', 'available']}}

now I want to store the status that is "available" in a variable with its key so that it can be used further for delete or update.

So the output I mean is like:

status={1001:available,1002:available,2001:available,2002:available}

Please help me by telling that how could I get this output.

CodePudding user response：

One approach is to use a dictionary comprehension:

rs = {ii : status for category in Book_list.values()  for ii, (name, status) in category.items() if status == "available"}
print(rs)

Output

{1001: 'available', 1002: 'available', 2001: 'available', 2002: 'available'}

The above is equivalent to the followings nested for loops:

for category in Book_list.values():
    for ii, (name, status) in category.items():
        if status == "available":
            rs[ii] = status

For understanding the unpacking expressions such as:

# _, category
# ii, (name, status)

you could read this link. For a general introduction to Python's data structures I suggest reading the documentation.

CodePudding user response：

def receive_available_books(Book_list):
    status = {}
    for cat in Book_list.values():
        for code, book  in cat.items():
            status[code] = book[1]
    return status

Output: {1001: 'available', 1002: 'available', 2001: 'available', 2002: 'available'}

CodePudding user response：

Using Python 3.10's structural pattern matching, maybe not super appropriate/helpful for this, but I just wanted to try it :-)

rs = {}
for category in Book_list.values():
    for item in category.items():
        match item:
            case ii, [_, 'available' as status]:
                rs[ii] = status

(code adapted from Dani's)