dict

Python has 4 basic inbuilt data structures: Lists, Tuples, Sets, and Dictionaries.

Lists, tuples, and sets are used to keep single elements in collections. Dictionaries, on the other hand, are used to keep key-value pairs. Similar to real-world dictionaries, where each word corresponds to its translation or explanation, Python dictionaries use keys to map them to their corresponding values. We can keep a dictionary of countries and their capitals:

capitals = {
    'Armenia': 'Yerevan',
    'Australia': 'Canberra',
    'Austria': 'Vienna',
    'Brazil': 'Brasilia',
    'United States': 'Washington D.C.',
}
print(capitals)
# {'Armenia': 'Yerevan', 'Australia': 'Canberra', 'Austria': 'Vienna', 'Brazil': 'Brasilia', 'United States': 'Washington D.C.'}

To define a dictionary, we first open a curly bracket {, then put each key on the left side of the colon :, and the value on the right side. Each key-value pair is separated by a comma, and the dictionary definition ends with a closing curly bracket }.

Both keys and values can be of different types. We can keep the city population in a dictionary:

population = {
    'Yerevan': '1M',
    'Canberra': 395790,
    'Vienna': '1.897 million',
    'Brasilia': 4804000,
    'Washington D.C.': 692683,
}
print(population)
# {'Yerevan': '1M', 'Canberra': 395790, 'Vienna': '1.897 million', 'Brasilia': 4804000, 'Washington D.C.': 692683}

In the case of lists and tuples, we could access the individual elements by their index [2]. When working with dictionaries, the access to elements is done through keys:

print(population['Yerevan'])    # 1M
print(population['Brasilia'])   # 4804000
print(population['New York'])   # KeyError: 'New York'
print(population[0])            # KeyError: 0

If the key does not exist in the dictionary, Python raises an error telling that the key is not in the dictionary.

Challenge

Google translate is great but can you create a simpler version of it?

You are helping your friend to study the French class. He is an English speaker, so you want to write a program for him that given an English word or a phrase would print the corresponding phrase in French. Below are the phrases that he’s currently studying:

Note: Don’t use if/else statements. It’s much shorter and easier to do this with dictionaries.

The input contains a single line - the phrase in English.

The program should print the corresponding French sentence.