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Combining dictionary and list¶

By combining dictionaries and lists in a single object many powerful data structures can be constructed depending on the application. Some illustrative examples follow.

Dictionary with lists as values¶

In the following example lists are used as values in a dictionary
The key:value pairs of the dictionary are of the form:
```
  {Code: [CountryName, Capital, Population]}
```
We use pprint.pprint() method to print the dictionary in a more readable format
Also string upper() method is used to capitalize user's input

import pprint
country = {}
country['GR'] = ['Greece', 'Athens', 11]
country['IT'] = ['Italia', 'Rome', 61]
country['ES'] = ['Spain', 'Madrid', 46]

pprint.pprint(country)

# Indexing: [Key][Integer], for example:  
print(country['GR'][1])

while 1:
    sel = input("Enter country code ('q' to Quit): ")
    if sel == 'q':
        break
    else:
        if sel.upper() in country:
            print(country[sel.upper()])

{'ES': ['Spain', 'Madrid', 46],
 'GR': ['Greece', 'Athens', 11],
 'IT': ['Italia', 'Rome', 61]}
Athens
Enter country code ('q' to Quit): GR
['Greece', 'Athens', 11]
Enter country code ('q' to Quit): q

Dictionary with dictionaries as values¶

Dictionaries can also be used as values in a dictionary
Below the dictionary key:value pairs are of the form:
```
  {Code:{CountryName:, Capital:, Population:]}
```

country = {}
country['GR'] = {'Name':'Greece',
                'Capital':'Athens',
                'Pop':'11 milions'}
country['IT'] = {'Name':'Italy',
                'Capital':'Rome',
                'Pop':'61 milions'}
country['ES'] = {'Name':'Spain',
                'Capital':'Madrid',
                'Pop':'46 milions'}

# Indexing: [Key][Key], for example:  
print(country['GR']['Capital'])

# print the country name and population for all countries
for c in country:
    print('Country: ',country[c]['Name'],'\tPopulation: ',country[c]['Pop'])

Athens
Country:  Italy 	Population:  61 milions
Country:  Greece 	Population:  11 milions
Country:  Spain 	Population:  46 milions

Lists of dictionaries¶

In the following example dictionaries are used as list items

import pprint
country={}
country['GR'] = {'Name':'Greece',
                'Capital':'Athens',
                'Pop':11}
country['IT'] = {'Name':'Italy',
                'Capital':'Rome',
                'Pop':61}
country['ES'] = {'Name':'Spain',
                'Capital':'Madrid',
                'Pop':46}

# Construct a list with dictionary items
Europe=[country[k] for k in country]
pprint.pprint(Europe)

# Indexing:[Integer][Key], for example:  
print(Europe[0]['Capital'])

# Print country name and capital city
for c in Europe:
    print('Country: ',c['Name'],'\tCapital: ',c['Capital'])

[{'Capital': 'Rome', 'Name': 'Italy', 'Pop': 61},
 {'Capital': 'Athens', 'Name': 'Greece', 'Pop': 11},
 {'Capital': 'Madrid', 'Name': 'Spain', 'Pop': 46}]
Rome
Country:  Italy 	Capital:  Rome
Country:  Greece 	Capital:  Athens
Country:  Spain 	Capital:  Madrid

(4) Google maps API¶

Several web services make APIs available using a combined list-dictionary structure
For example, Google maps API returns geographical information organized in complex list-dictionary structure
The geo object below is only a selected part of the whole object returned

geo = [{'address_components': [{'name': 'WHITE TOWER',
                                'types': ['point_of_interest', 'establishment']},
                               {'name': 'Thessaloniki',
                                'types': ['locality', 'political']},
                               {'formatted_address': 'WHITE TOWER, Thessaloniki 546 21, Greece',
                                'geometry': {'location': {'lat': 40.6257895, 'lng': 22.9495735},
                                             'place_id': 'ChIJN4DZEQM5qBQRULmG-uTW4-c',
                                             'types': ['bus_station',
                                                       'transit_station',
                                                       'point_of_interest',
                                                       'establishment']}}]}]

Practice¶

Using the geo object above try to answer the following questions (write also the code to present onscreen the appropriate values):
1. What is the type of the geo object?
2. How many items does geo contain?
3. What is the value object for the key 'address_components'?
4. How many items and of what type does the above value object contain?
5. What is the length of the 3rd item of the above mentioned value object?
6. Write a print to present onscreen the value of the key 'lat'
7. Write a print to present onscreen the last item of the value object with key 'types'

Copyright¶

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