Python Basics

Deanne, Seifu

Why use Python?

print ("Hello World!")

Basic Syntax

from time import localtime

activities = {
  8: 'Sleeping',
  9: 'Commuting',
  17: 'Working',
  18: 'Commuting',
  20: 'Eating',
  22: 'Resting'
}

time_now = localtime()
hour = time_now.tm_hour

for activity_time in sorted(activities.keys()):
  if hour < activity_time:
    print(activities[activity_time])
    break
  else:
    print('Unknown or sleeping!')

Numbers and Strings

  • floating point: 3.14159
  • integer: 4
  • string: "This is a string"

    • Numbers and Strings Exercise

      Change the code to create a string "hello" and floating number 10 and an integer of 20 
      #change this code
		mystring = None
		myfloat = None
		myint = None

		#testing code
		if mystring == "hello":
			print ("String: %s" %mystring)
		if isinstance(myfloat, float) and myfloat == 10.0:
			print ("Float: %d" % myfloat)
		if isinstance (myint, int) and myint == 20:
			print ("integer: %d" % myint)

    Lists

    L = [123, 'spam', 1.23]

		len(L)

		L[0]

		L[:-1]

		L + [4.5,6]

		L.append('NI')
		L.pop(2)

    M = [[1, 2, 3],
		    [4, 5, 6],
		    [7, 8, 9]]
		M[1]
		M[1][2]

    List Exercise

    Add numbers 1, 2, 3 to the numbers list Add hello and world to the strings variable Fill in variable second_name with the second names in the names list 

    numbers = []
strings = []
names = ["John", "Eric", "Jessica"]

# write your code here
second_name = None


# this code should write out the filled arrays and the second name in the names list (Eric).
print(numbers)
print(strings)
print("The second name on the names list is %s" % second_name)

    Tuples

    T = (1, 2, 3, 4)

len(T)

T + (5, 6)

T[0]

T.index(4)

T.count(4)

    T = 'spam', 3.0, [11, 22, 33]

T[1]

T[2][1]

    Dictionary

    Creating a dictionary

    emp1 = {'name': 'Bob', 'job': 'waiter', 'salary': 3}

    emp1 = dict(name='Bob', job='waiter',salary=3)

    emp1 = {}
emp1['name'] ='Bob'
emp1['job'] = 'waiter'
emp1['salary'] = 3

    Nesting in a dictionary

    emp1 = {'name': {'first': 'Bob', 'last': 'Smith'}, 'jobs':['waiter', 'host'], 'salary': 3

    Dictionary Exercise

    Add "Jake" to the phonebook with the phone number 938273443, and remove Jill from the phonebook

    phonebook = {
    "John" : 938477566,
    "Jack" : 938377264,
    "Jill" : 947662781
    }

# write your code here


# testing code
if "Jake" in phonebook:
    print ("Jake is listed in the phonebook.")
if "Jill" not in phonebook:
    print ("Jill is not listed in the phonebook.")

    Basic Operators

    Numbers

    Follows basic order of operations

    x = 40
x/20 + 17*10**2

    Strings

    myStr = "Hello world!"
print (myStr[0])
print (myStr[0:3])

    Comparison

    Often used with if, for and while statements

  • ==, !=, <>, >, <, <=,>= 
    • if isinstance (myint, int) and myint == 20:
				print "integer: %d" % myint

    Assignment

    For simplifying code

  • =, +=, -=,*=, /=, %=, **=, //=
  • a = a%b is equivalent to a %=b

    • Introduction to Functions

    A function includes the 'def' keyword 

    'Arguments are optional in the function'
def functionName (optArg1,optArg2, ...):
    'set something'
    'return something'
    'print something'

    Some examples

    def printFunction (username, greeting):
    print ("Hello, %s, From My Function, I wish you %s"%(username, greeting)")

    def sumFunction (x,y):
    return x + y