Arithmetic Operations



In [1]:

    
2 + 2









    Out[1]:





4



In [2]:

    
(1 + 3) * 4









    Out[2]:





16



In [3]:

    
cups_of_flour = 5
cups_of_flour * 0.5









    Out[3]:





2.5



In [4]:

    
1/2









    Out[4]:





0



In [5]:

    
1.0/2









    Out[5]:





0.5



In [6]:

    
1/2.0









    Out[6]:





0.5



In [7]:

    
"Hello" + 1









    



---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-7-465e48023fdd> in <module>()
----> 1 "Hello" + 1

TypeError: cannot concatenate 'str' and 'int' objects



In [ ]:

    
"Hello" + str(1)



In [ ]:

    
"Hello" + `1`



In [ ]:

    
"hello" * 5

What is None?



In [8]:

    
a = 1
a









    Out[8]:





1



In [9]:

    
a = None
a



In [10]:

    
not None









    Out[10]:





True



In [11]:

    
None != False









    Out[11]:





True

Control Statements

Note: Python uses indentation to group things.



In [12]:

    
if 2 > 1:
    print "Hello World!"









    



Hello World!



In [13]:

    
if 1 > 2:
    print "Hello World!"
else:
    print "World is not a beautiful place!"









    



World is not a beautiful place!



In [14]:

    
if 1 > 2:
    print "Hello World!"
elif 2 > 3:
    print "World is even better!"
elif 3 > 4:
    print "I don't want to live here!"
else:
    print "World is not a beautiful place!"









    



World is not a beautiful place!



In [15]:

    
a = None
if a is None:
    print "a is None"
else:
    print "a is not None"
    
b = 10
if b == None:
    print "b is None"
else:
    print "b is not None"









    



a is None
b is not None

if / else with strings and lists



In [16]:

    
list1 = [1, 2, 4, 2, 100]
s = "Hello world"



In [17]:

    
if 4 in list1:
    print "Hey! 4 exists in list1"









    



Hey! 4 exists in list1



In [18]:

    
if 2 in list1:
    i = list1.index(2)
    print "Search successful. Found at index {0}".format((i+1))









    



Search successful. Found at index 2



In [19]:

    
if 'o' in s:
    print "'o' exists!"









    



'o' exists!



In [20]:

    
if 'llo' in s:
    print "'llo' exists!"









    



'llo' exists!



In [21]:

    
if 'house' not in s:
    print "house not found!"









    



house not found!

Exercise

Q. Six is a Mob

Create a list with at least 6 names inside it. Write an if/else test case to test the following

If there are more than 5 people, a message is printed about there being a mob in the room.
If there are 3-5 people, a message is printed about the room being crowded.
If there are 1 or 2 people, a message is printed about the room not being crowded.
If there are no people in the room, a message is printed about the room being empty.

Loops

while loop
for loop

While loop syntax

while <condition>:
    # do something
    # do something



In [22]:

    
count = 0
while count < 10:
    print count
    count += 1  # count = count + 1

An infinite loop

while <a true condition>:
    # do something

a true condition can be anything which evaluates to True e.g. True, 1, not False, etc.

Nested while loops



In [23]:

    
i = 0;
while i < 5:
    j = 5;
    while j > 0:
        print i, j
        j -= 1
    i += 1

Using break, pass and continue



In [24]:

    
count = 0
while count < 10:
    print count
    count += 1  # count = count + 1
    if count == 5:
        break



In [25]:

    
count = 0
while count < 10:
    count += 1  # count = count + 1
    if count < 5:
        continue
    print count



In [26]:

    
count = 0
while count < 10:
    print count
    count += 1  # count = count + 1
    if count < 5:
        pass
    else:
        break