根据用户从字典中输入的信息来提取信息

Question

I have the following information from a .json loaded and stored in a variable Data :

Data = [
    {u'rating': u'89', u'rare': u'1', u'name': u'Pogba', u'club_image': u'/content/fifa17/img/clubs/11.png', u'image': u'/content/fifa17/img/players/195864.png', u'rare_type': u'3', u'version': u'IF', u'full_name': u'Pogba', u'position': u'CDM', u'id': u'15073', u'nation_image': u'/content/fifa17/img/nation/18.png'},
    {u'rating': u'89', u'rare': u'1', u'name': u'Pogba', u'club_image': u'/content/fifa17/img/clubs/11.png', u'image': u'/content/fifa17/img/players/195864.png', u'rare_type': u'21', u'version': u'OTW', u'full_name': u'Pogba', u'position': u'CM', u'id': u'15091', u'nation_image': u'/content/fifa17/img/nation/18.png'},
    {u'rating': u'88', u'rare': u'1', u'name': u'Pogba', u'club_image': u'/content/fifa17/img/clubs/11.png', u'image': u'/content/fifa17/img/players/195864.png', u'rare_type': u'1', u'version': u'Normal', u'full_name': u'Pogba', u'position': u'CM', u'id': u'78', u'nation_image': u'/content/fifa17/img/nation/18.png'}
]

I'd like to extract the information depending on the rating of the player inputted by the user, only if another rating exists . EDIT : By this, I mean that if only one line was present, ie 1 rating, there would be no need to carry out the process.

For example, if the user inputted: 88 , it would return/print:

{u'rating': u'88', u'rare': u'1', u'name': u'Pogba', u'club_image': u'/content/fifa17/img/clubs/11.png', u'image': u'/content/fifa17/img/players/195864.png', u'rare_type': u'1', u'version': u'Normal', u'full_name': u'Pogba', u'position': u'CM', u'id': u'78', u'nation_image': u'/content/fifa17/img/nation/18.png'}

From my minimal knowledge, I am aware that I must use dictionaries, but am unaware of how to do so. However, I am currently in the following stage in my attempts:

player_dict = {Data}
player_info = player_dict.get(user_input)
if player_info:
    for item in player_info:
        player_info = item

^ This doesn't seem to work at all.

Answer 1

Well in this case, you need to loop over your values and compare the one that has been input to the ones you already have, right?

So player_dict is a list of dictionaries, and every dictionary contains properties about a player, of which rating is one. Also, let's say that player_info is the user-inputted rating, like 88 .

for player_dict in player_dict:
    try:
         if player_dict['rating']==player_info:
              return player_dict
    except KeyError:
         print 'there is no key called rating in this dict!'

Answer 2

You can use list comprehensions:

[record for record in Data if record.get("rating") == ratingWeWant]

where ratingWeWant is the rating you are searching for.

That code will produce list of records from data that have specified rating, eg:

[{u'rating': u'88', u'club_image': u'/content/fifa17/img/clubs/11.png', u'image': u'/content/fifa17/img/players/195864.png', u'full_name': u'Pogba', u'id': u'78', u'nation_image': u'/content/fifa17/img/nation/18.png', u'rare': u'1', u'name': u'Pogba', u'rare_type': u'1', u'version': u'Normal', u'position': u'CM'}]

for data in your post.

Also, because we use .get() method of dict, we don't have to worry about exceptions.

Answer 3

What you are trying to do is called a "lookup". Given a key (u'88', or other rating), you want a value (the dictionary where 'rating' is u'88'). A list object, like you currently have the dictionaries stored in, is not very good for such lookups, because you have to go through each index in the list, compare the rating to the key, and then return the dictionary (if it exists at all).

key = u'88'
for d in Data:
    if d['rating'] == key:
        print d

Consider what happens when you have a large amount of dictionaries stored in that list. What if none of the dictionaries have a rating equal to the key? You pass through a large number of dictionaries, checking for equalities, only to have none exist. This is wasted computations.

As you know, python's dict type is very-well suited for lookups. If you had a dictionary that looked like

Data_dict = {u'88': {u'rare': u'1', u'name': u'Pogba', ...},
             u'89': {u'rare': u'1', u'name': u'Pogba', ...} }

then you could quickly see if the key u'88' is in that dataset.

if u'88' in Data_dict:
    print Data_dict[u'88']

To make such a dictionary, from your current Data as a list:

Data_dict = {val[u'rating']: val for val in Data}

Answer 4

The other answers don't include your requirement that data should only be returned if the rating appears in Data once only.

# First iterate over Data and count how many times that rating appears
counter = {}
for item in Data:
    rating = item['rating']
    counter[rating] = counter.get(rating, 0) + 1

# Now build a dict that uses rating as a key and the whole dataset with  
# that rating as a value. Include only ratings that appeared once in Data
cleaned_dict = {item['rating']: item for item in Data if counter.get(item['rating']) == 1}

query = raw_input('Enter rating:')

if cleaned_dict.get(query):
    print "FOUND"
    print cleaned_dict.get(query)
else:
    print "Not found, no need to process further"

Explanation:
In the first for loop, we build a dictionary of {rating: frequency} . The line counter[rating] = counter.get(rating, 0) + 1 says that if the rating isn't in the dictionary, give that rating a default count of 0 and immediately add 1 to it. ie it appears once. If, however, later in the for loop we find that rating again, we get the value stored against that rating and add 1 to it. You could also use the Counter object for this but I've found that usually to be slower to get() .

In cleaned_dict we use a dictionary comprehension to build a new set of data only if that rating appeared once in Data . We store the whole raw data against a key of just the rating . This allows fast lookup on user input.

Finally, we take user input and look for the rating in our dictionary. If the rating is not a key in cleaned_data then we get None , which is falsey, so if cleaned_dict.get(query): is interpreted as False .

EDIT based on comments:

cleaned_dict = {}
for item in Data:
    rating = item['rating']
    is_in_dict = cleaned_dict.get(rating)
    if is_in_dict:
        position = item['position']
        cleaned_dict[rating][position] = item
    else:
        sub_dict = {}
        sub_dict[item['position']] = item
        cleaned_dict[rating] = sub_dict

rating_input = raw_input('Enter rating:')
check_rating = cleaned_dict.get(rating_input)
if check_rating:
    position_input = raw_input('Enter position:')
    if check_rating.get(position_input):
        print check_rating.get(position_input)
    else:
        print "Record of rating, but not position"
else:
    print "No record of rating {}".format(rating_input)