if Statement

if x < 0:
    # Action 1
elif x == 0:
    # Action 2
elif x == 1:
    # Action 3
else:
    # Action 4

for Statement

devices = ['computer', 'phone', 'printer']
for elements in devices:
	print elements, len(elements)

# Output:
 

computer 8
phone 5
printer 7

range() Function

If you do need to iterate over a sequence of numbers, the built-in function range() comes in handy. It generates lists containing arithmetic progressions:

range(10)
 



# Output:


 

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

range(5, 10)
 

# Output:


 

[5, 6, 7, 8, 9]

range(0, 10, 3)
 

# Output:
 
[0, 3, 6, 9]

range(-10, -100, -30)


 

# Output:
 

[-10, -40, -70]

To iterate over the indices of a sequence, combine range() and len() as follows:

sentence = ['Tom', 'is', 'a', 'nice', 'guy']
for i in range(len(sentence)):
      print i, sentence[i]


 


# Output:
 

0 Tom
1 is
2 a
3 nice
4 guy

Defining Functions

We can create a function like follows:

def sum(a,b):    # returns a+b
     return a+b
 
# Now call the function we just defined:
sum(2,43)
 

# Output:
 

45