Common uses for Dictionaries

Introduction to Python Dictionaries

Common uses for Dictionaries

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Common Uses for Python Dictionaries

Review

They are Python’s built-in mapping type. They map keys, which can be any immutable type, to values, which can be any type (heterogeneous), just like the elements of a list or tuple. In other languages, they are called associative arrays since they associate a key with a value.

Example Dictionary to Translate

As an example, lets create a dictionary to translate English words into Spanish. Since we will be dealing with word, the keys will be strings in this case.

One way to create a dictionary is to start with the empty dictionary and add key:value pairs. As seen in the previous card, the empty dictionary is denoted {}. Below, I will begin to create the dictionary that we can use for translation.

            
# Initialize the dictionary englist2spanish = {} # Add the values for 1 & 2 englist2spanish["one"] = "uno" englist2spanish["two"] = "dos" #Print out the result print(englist2spanish)

Example Python Dictionary to look up specific Rainfall for a year

We could think of a situation where we want to look up the rainfall by a specific year. In this case, a python dictionary would be a great resource as we can use the year for the key and the percentage of rainfall as the value. Below is an example of this in action!

            
# Create the dictionary rain_percent = { 1980: '17%', 1981: '15%', 1982: '10%'} # Print out the whole thing print(rain_percent) # Look up based on specific year print(rain_percent[1980]) # Output: # {1980: '17%', 1981: '15%', 1982: '10%'} # 17%

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In the next card we will look at some what python dictionaries cannot achieve but also we will look at some of the other powerful methods that can be sued with python dictionaries.

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