The first time we encounter a word, we initialize its count to zero.
We know we encounter it for the first time because there is no dictionary key for them yet.
Python dictionary is one of the built-in data types. There is no explicitly defined method to add a new key to the dictionary.
If you want to add a new key to the dictionary, then you can use assignment operator with dictionary key.
Example cases where you could use a Python dictionary: Not everything can be a dictionary key, for example lists cannot.
(If you're interested in the details: It's because lists are "mutable", that is, you can change individual items on a list, and that would mess up the way dictionaries are represented internally in Python.)What can be a dictionary value? Here is again our first example, where the dictionary values were strings: Can you use it to do a bad translation of the following German sentence?The Nietzschean diet, which commands its adherents to eat superhuman amounts of whatever they most fear, is developing a strong following in America.”””.Note that this is a variant of the "accumulation" code pattern that you have seen before. Then we iterate over the words in the paragraph, adding numbers to the dictionary as we go along.mysent = "vom eise befreit sind strom und baeche"Here's a solution: (Note that this is not how you want your machine translation to work!The translations that you get this way are terrible.)paragraph = ”””While dieters are accustomed to exercises of will, a new English translation of Germany's most popular diet book takes the concept to a new philosophical level. It uses the words as keys, and their counts as the values.(Of course, that only works if you know exactly how long the list or tuple is.)Usually when doing assignments, assigning the right-hand side of the "=" to the left-hand side, there was only a single variable on the left-hand side.But if we know that the right-hand side of the "=" has exactly two components, we can put two variables on the left-hand side.To understand the difference between mutable (changable) and immutable (unchangable), it’s helpful to look at how Python actually treats these variables.Let’s start by considering a simple variable assignment: toward a different list, we’re directly updating the existing list: Even if we create multiple list variables, as long as they point to the same list, they’ll all be updated when that list is changed, as we can see in the code below: Here’s an animated visualization of what’s actually happening in the code above: This explains why our global variables were changed when we were experimenting with lists and dictionaries earlier.We’ll also use the variable names as the function’s parameter names.Then, we’ll see whether all of the variable usage inside our function has affected the global value of these varaibles.