This cheatsheet has some of the tips and tricks for using the Python programming language. As I learn more about Python, I will post more useful code snippets here in order to help you.
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Table of Contents
Math and Numbers
Running Python Scripts
python <script name>
<script name> with the file name of the Python script that you want to run.
Variables hold the values that are used in your application or script. In Python, variables are not strong-typed. This means that the variables you declare, are not limited to a particular data type. However, the variable does have a value, any future changes to that value must be of the same type. So you cannot set the value of a variable to a string and then change it to a integer.
myVariable = "red" myOtherVariable = false myOtherOtherVariable = 5
To write a function in Python, you start the function out with the "def" keyword.
def myFunction (param1, param2, param3): sum = param1 + param2 + param3 return sum
If you notice, there are no braces or brackets around the contents of the function. Python relies on indentation for the grouping of lines together within a given section.
Random nubmers can be used to do countdowns or other things that are needed. To get a random number, you have to import the randomint class from the random library by adding
from random import randint
to the top of your Python script.
Then you can set the random integer to a variable by doing
myNumber = randint(5,60)
In the example above, 5 is the lower limit of the range and 60 is the upper limit of the range. If your range needs to be different, then changes either or both of these values.
To do addition in Python, just have to code out two numbers and add them together like you would normally do for a math problem that you were writing on paper. Just keep in mind that the calculations always have to be done on the right side of the equals sign and will be set to the variable on the left of the equals sign.
sum = 5 + 3 print sum
Similar in fashion, subtraction is written just like addition, except it uses the minus sign instead of the plus sign.
difference = 10 - 3 print difference
Multiplication is done using the asterisk.
product = 4 * 3 print product
quotient = 20 / 5 print quotient
Below is a sample of how to print out "Hello world" in Python.
print ("Hello world")
The Raspberry Pi traffic light project is written in Python code. You can review the code at https://github.com/almostengr/raspitraffic-stem.