Unlike human languages, the Python vocabulary is actually pretty small. We call this “vocabulary” the “reserved words”. These are words that have very special meaning to Python. When Python sees these words in a Python program, they have one and only one meaning to Python. Later as you write programs you will make your own words that have meaning to you called variables. You will have great latitude in choosing your names for your variables, but you cannot use any of Python’s reserved words as a name for a variable.
In a sense, when we train a dog, we would use special words like, “sit”, “stay”, and “fetch”. Also when you talk to a dog and don’t use any of the reserved words, they just look at you with a quizzical look on their faces until you say a reserved word. For example, if you say, “I wish more people would walk to improve their overall health.”, what most dogs likely hear is, “blah blah blah walk blah blah blah blah.” That is because “walk” is a reserved word in dog language. Many might suggest that the language between humans and cats has no reserved words1.
The reserved words in the language where humans talk to Python incudes the following:
and del for is raise assert elif from lambda return break else global not try class except if or while continue exec import pass yield def nally in print
That is it, and unlike a dog, Python is already completely trained. When you say “try”, Python will try every time you say it without fail.
We will learn these reserved words and how they are used in good time, but for now we will focus on the Python equivalent of “speak” (in human to dog language). The nice thing about telling Python to speak is that we can even tell it what to say by giving it a message in quotes:
print 'Hello world!'
And we have even written our first syntactically correct Python sentence. Our sentence starts with the reserved word print followed by a string of text of our choosing enclosed in single quotes.