Python Statements

if..elif..else

The "if..elif..else" statement is used for decision making based on some conditions.

if statement

The syntax of "if" statement is

if test expression:
    statement(2)



In [1]:

    
x = 1
if x > 0:
    print(x,"is positive number")









    



1 is positive number

Pls note the indentation is important in Python. All the statements that is part of if statement must be indented.



In [2]:

    
x = 1
if x > 0:
    print(x,"is positive number")
print('Outside of if condition')









    



1 is positive number
Outside of if condition

if..else.. statement

if test expression:
    # body of if
else:
    # body of else



In [3]:

    
x = 1
if x >= 0:
    print(x,"is positive number")
else:
    print(x,"is negative number")
    
print('End of if..else..')









    



1 is positive number
End of if..else..

if..elif..else statement

if test expression:
    # body of if
elif test expression:
    # body of elif
else
    # body of else



In [4]:

    
x = -5
if x == 0:
    print(x,"is zero")
elif x > 0:
    print(x,"is positive")
else:
    print(x,"is negative")
    
    
print('End of if statement')









    



-5 is negative
End of if statement

Nested if



In [5]:

    
x = 8
if x == 0:
    print(x,"is zero")
elif x > 0:
    if x == 10:
        print(x,"is equal to 10")
    elif x > 10:
        print(x,"is greater than 10")
    else:
        print(x,"is lesser than 10")
else:
    print(x,"is negative")
    
    
print('End of if statement')









    



8 is lesser than 10
End of if statement

for loop

The for loop statement is used to iterate over a sequence data type or other iterable objects. Iterating over a sequence is called traversal.

Loop continues until the condition is met or the last item in the sequence is processed.

for val in seq:
    # body of for



In [6]:

    
sum = 0             # variable to hold the sum
nums = [1,2,3,6,8]  # list of numbers

for num in nums:
    sum += num
    
print(sum)

for loop with else



In [7]:

    
digits = [0,1,5]

for i in digits:
    print(i)
else:
    print('No more digits to print')









    



0
1
5
No more digits to print

Range Function

Range function is used to generate sequence of numbers. For example range(5) will generate 5 numbers starting from 0 to 4.

The syntax for range function is: range(start,stop,increment)



In [8]:

    
# range function with required sequence of numbers
print(range(10)) # this will not print sequence of numbers but generated on the fly.

# range function to start with 1 to 10 (note the stop argument is always treated as stop -1)
print(list(range(1,11)))

# range function different start and stop
print(list(range(2,8)))

# range function with start,stop and increment parameters
print(list(range(0,10,2)))









    



range(0, 10)
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
[2, 3, 4, 5, 6, 7]
[0, 2, 4, 6, 8]



In [9]:

    
colors = ['Blue','White','Green']
for i in range(len(colors)):
    print('I like',colors[i],'color')









    



I like Blue color
I like White color
I like Green color

While

While loop is used to iterate over a block of code as long as the test expression is true. Please note in python any non-zero value is True and zero is interpreted as False.

Mainly used when we do not know how many times to iterate

while test_expression:
    # body of while



In [14]:

    
sum = 0
i = 1
while i <= 10:
    sum += c
    i += 1
    
print(sum)



In [11]:

    
n = 5
sum = 0
i = 1
while i <= n:
    sum += i
    i += 1
    
print(sum)

While...else

The "else" part is executed when the while condition evaluates to false.

The "else" part occurs if no break occurs and the condition is false.



In [15]:

    
counter = 0
while counter < 3:
    counter += 1
    print('Inside Loop')
else:
    print('Inside Else')









    



Inside Loop
Inside Loop
Inside Loop
Inside Else

Break Statement

The break statement terminates the loop containing it. The control of the program flows to the statement immediately below the loop.



In [17]:

    
for val in "string":
    if val == "i":
        break
    print(val)  
        
print("The End")









    



s
t
r
The End

Continue Statement

The continue statement is used to skip the rest of the code inside a loop for the current iteration only. Loop does not terminate but continues on with next iteration.



In [18]:

    
for val in "string":
    if val == "i":
        continue
    print(val)
    
print("End Loop")









    



s
t
r
n
g
End Loop

Pass Statement

Pass statement is generally used as a placeholder for loop or function or classes as they cannot have empty body. So "Pass" is used to construct the body that does nothing.

The difference between comment (#) and "pass" is that python interpreter ignores the comments while it treat "pass" as no operation.



In [19]:

    
def dummy():
    pass

dummy()



In [20]:

    
for i in range(3):
    pass