Table of Contents

Exercise 2 : Python Basics

Output to terminals

print “hello world”
print 1+1

Variables

integer, strings, float
convert integer to strings and vice versa
- str(5)
- int(age)
5/3 = 1.6666(float) or 1(int)
calculate the string length len()

Declaration (Comments)

# comments out a line of code
“”“ paragraph ”“” comments out one or more lines of code

Statement

age = 10
print age

Keywords

The following is a list of keywords for the Python programming language.

and	del	from	not	while
as	elif	global	or	with
assert	else	if	pass	yield
break	except	import	print	class
exec	in	raise	continue	finally
is	return	def	for	lambda
try

 import keyword
 print "Python keywords: ", keyword.kwlist

Operators

Symbol	Type	What it Does
+	Mathematical	Addition
-	Mathematical	Subtraction
*	Mathematical	Multiplication
/	Mathematical	Division
%	Modulos	Returns the remainder from a division
&	Logical	And
pipe	Logical	Or
«	Shift	Left Shift
»	Shift	Right Shift
~	Logical	Bitwise Negation
<	Comparison	Less than
>	Comparison	Greater than
==	Comparison	Equal to
!=	Comparison	Not Equal To
>=	Comparison	Greater than or Equal To
⇐	Comparison	Less than or Equal To
=	Assignment	Assigns a value
+=	Assignment	Adds and assigns a value
-=	Assignment	Subtracts and Assigns a value
*=	Assignment	Multiplies and assigns a value
/=	Assignment	Divides and assigns a value
%=	Assignment	Modulus and assigns
»	Assignment	Shifts and assigns
«	Assignment	Shifts and assigns
And	Boolean
Or	Boolean
Not	Boolean

other operators are

TruncatingDivision                   [//]
Mathematical Powers                  [**]
Bitwise XOR                          [^]
Truncate Divides and assigns a value [//=]
Powers and assigns                   [**=]

Functions() and importing

def increment(x):
  return x+1
  
import math
  math.sqrt(4)

Always remember the flow of execution - the identation

Conditions and Recursions

Boolean & logical expressions
- 26 == 26
- True
- !=, >, <; >=, ⇐, %, and, …

Alternative executions
- if, else, elif,
- Nested layers

return, continue

Iterations/loops

while n > 20:
for i in range(0, 20):
for char in fruit:

  while i < n:
      print txt
      
  for x in range(0,20):
       print x*x
  fruit = "Banana"
  for char in fruit:
      print char

Nested loops

  for x in xrange(1,11):
  for y in xrange(1,11):
      print '%d * %d = %d' % (x,y,x*y)

Early exit

  for x in xrange(3):
  if x==1:
      break

For..Else

  for x in xrange(3):
      print x
  else:
      print 'Final x = %d' % (x)

Strings as an iterable

  string = "Hello World"
  for x in string:
      print x

Lists as an iterable

  collection = ['hey',5,'d']
  for x in collection:
      print x

Lists of lists

 list_of_lists = [ [1, 2, 3], [4, 5, 6], [7, 8, 9]]
 for list in list_of_lists:
    for x in list:
        print x

Creating your own iterable

  class Iterable(object):
     def __init__(self,values):
        self.values = values
        self.location = 0
     def __iter__(self):
        return self
     def next(self):
        if self.location == len(self.values):
            raise StopIteration
        value = self.values[self.location]
        self.location += 1
        return value