3. Statements and Expressions
Programs we write will be made up of multiple lines of code
Each line will be doing some sort of work/computation
A statement is an instruction for Python to do something
If you type a series of statements and press run, Python does what you asked (or at least tries to)
Some statements result in some immediate output
Others will do some work behind the scenes
some_variable = 5
An expression is, roughly, a statement that can be crunched down to a value
More precisely, an expression is a combination of
literal values (e.g.,
some_other_variable = (some_variable + 1) * 2is an example of an expression (and statement)
We have been using these in our code already
Operators are symbols that tell Python to perform computations on expressions
example arithmetic operators —
Generate expressions to:
Add two variables together (use whichever values you want) and save the result to some variable.
Multiply two variables together and save the result to some other variable.
Divide result of step 2 by the result of step 1.
Add a third variable to the result of step 3.
Now for a tougher one. Convert a temperature from Celsius to Fahrenheit.
3.4. Operators On Other Types
There are operators for values other than just numbers
We will see many of these as we move through the course
Experiment with the operators you know on strings (instead of just integers).
Which ones work? What do they do?
Try mixing strings and integers with various operators. What happens there?
3.5. Large Series of Statements
So far we have been writing programs that are about one line long
There is nothing stopping us from writing large programs with many lines of code
Saved in Colab or some other file
We often call these Python programs scripts
Python will run each line of the program, one line at a time, in the order that they exist
Technically you can write your script in any text editor, but there are editors/environments designed for programming languages
Colab (use through the internet)
Sublime (Windows and Mac)
PyCharm (Windows, Linux, and Mac)
VS Code (Windows, Linux, and Mac)
Consider the sentence “I am taking CSCI 161”. Write a program that stores each word of that sentence in it’s own
variable, and then prints the whole sentence to the screen, using only a single
3.6. For Next Class
If you have not yet, read the rest of Chapter 2 of the text