Basics

• in shell do python3 to open the command line
• python3 skript.py to execute a .py skript

Installing pip

• due to the version chaos that is pip pip3 python and python3, here an explanation
• stick with python 3
• so if a site tells you to do pip install do pip3 install

# installing the pip3 from python3.X (not pip from python 2.7)
sudo apt-get install python3-pip ## use the apt-get for now
# example of a pip install, DONT use sudo here
pip3 install pylama pylama-pylint

Special rules

• you can split a single line like this into multiple lines using \

total = item_one + \
   item_two + \
   item_three

Commands

#!/usr/bin/python3
print("test") #basically like echo, includes \n

input("\n\nPress the enter key to exit.") #creates a user prompt, has two empty lines before

; # ";" is used like in shell to get more commands in one line

Variables in python3

Usually Class names start with an uppercase letter All other identifiers start with a lowercase letter Starting an identifier with a single leading underscore indicates that the identifier is private don't use words like for etc for it A few examples:

Numeric Variables

#!/usr/bin/python3

counter = 100           # An integer assignment
miles   = 1000.0        # A floating point
name    = "John"        # A string
cplx = 70.2-E12         # complex number
# also possible to add one input to multiple variables
a = b = c = 1
#or like an oneliner array (so a get 1 b 2 etc.)
a, b, c = 1, 2, "john"
# delete them with
del counter, miles

String Variables

#!/usr/bin/python3

str = 'Hello World!'

print (str)          # Prints complete string, starts at 0
print (str[0])       # Prints first character of the string
print (str[2:5])     # Prints characters starting from 3rd to 5th
print (str[2:])      # Prints string starting from 3rd character
print (str * 2)      # Prints string two times
print (str + "TEST") # works only on strings

List Variables

• works a bit like in R
• can store different variable types, can be changed
• a list works only with []
• a "read only" list is with()

#!/usr/bin/python3

list = [ 'abcd', 786 , 2.23, 'john', 70.2 ]
tinylist = [123, 'john']

print (list)          # Prints complete list
print (list[0])       # Prints first element of the list
print (list[1:3])     # Prints elements starting from 2nd till 3rd
print (list[2:])      # Prints elements starting from 3rd element
print (tinylist * 2)  # Prints list two times
print (list + tinylist) # Prints concatenated lists


tuple = ( 'abcd', 786 , 2.23, 'john', 70.2 )
# print works exactly the same here

• there is also a dictionary type of list with {} its basically unordered, so you can shove data into it
• check here

Loops

• are without braces, spacing and lines depends if it works
• examples:

for i in [1,2,3]:
    print(i) #only shows the variable
    print('%sbp' % i) #this is how to put variables and text together
    print("____")
print("loop is ended, wow")

#first line with : is called header, all of it is called suite
if expression :
   suite
elif expression :
   suite
else :
   suite