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1.3 Python Review: Loops, Sets, Tuples and Dictionaries

Loops

We’ll mainly use for loops in this course. Here’s the python syntax for a for-loop:

for i in range(a, b):

The range function produces a list of numbers between the starting number a to the ending number b. By cycling through all the numbers in this list, we run a loop these many times.

Run the next cell, which contains a for-loop to print every number between 1 and 9. In the next cell, write a for-loop to print the employee IDs of the employees mentioned in exampleDf.

Set

There are two easy ways to create a set. The first one is just a direct initialization:

set1 = {"item1", "item2", "item3"}

The second way involves using the set constructor to create a set:

set2 = set(("item1", "item2", "item3"))

Just like with Dictionaries, duplicates are not allowed. Sets don’t have a particular order and the set is unchangeable.

To get the length of a set:

len(set)

Tuples

A tuple is another way of storing many values in a single variable. Like with Sets, there are two ways to create a new tuple.

tupleOne = ("itemOne", "itemTwo", "itemThree", "itemFour")

The second way to create a tuple is using the tuple constructor.

tupleTwo = tuple(("itemOne", "itemTwo", "itemThree", "itemFour"))

The Same length method applies

len(tupleOne)

Dictionaries

A dictionary in Python is a lot like a dictionary in the real world. For every word, there’s a particular meaning associated. This is what a dictionary is like. You look for the word, and find its meaning. You’ll see the syntax to create a new dictionary in the next cell. You can run this.

A dictionary consists of two main parts, a key and a value. If you specify a particular key, you can extract the corresponding value from the dictionary. However, dictionaries don’t allow duplicate keys, for obvious reasons. If a real world dictionary contained two words with the same spelling, but different meanings, how would you know which one to reference?

dictionary["key"]

for example, provides the value at the particular key within the dictionary dict.

len(dictionary)

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