Python Control Flow, Functions: short important questions and answers

CONTROL FLOW, FUNCTIONS

1. Define Boolean expression with example.

A boolean expression is an expression that is either true or false. The values true and false are called Boolean values.

Eg :

>>>5 == 6

False

True and False are special values that belongs to the type bool; they are not strings:

2. What are the different types of operators?

·                 Arithmetic Operator (+, -, *, /, %, **, // )

·                 Relational operator  ( == , !=, <  >, < , > , <=, >=)

·                 Assignment Operator ( =, += , *= , - =, /=, %= ,**= )

·                 Logical Operator (AND, OR, NOT)

·                 Membership Operator (in, not in)

·                 Bitwise Operator (& (and), | (or) , ^ (binary Xor), ~(binary 1’s complement , << (binary left shift), >> (binary right shift))

·                 Identity(is, is not)

3. Explain modulus operator with example.

The modulus operator works on integers and yields the remainder when the first operand is divided by the second. In Python, the modulus operator is a percent sign (%). The syntax is the same as for other operators:

Eg:

>>> remainder = 7 % 3

>>> print remainder

1

So 7 divided by 3 is 2 with 1 left over.

4. Explain relational operators.

The == operator is one of the relational operators; the others are:

X! = y # x is not equal to y

x > y # x is greater than y

x < y # x is less than y

x >= y # x is greater than or equal to y

x <= y # x is less than or equal to y

5. Explain Logical operators

There are three logical operators: and, or, and not. For example, x > 0 and x < 10 is true only if x is greater than 0 and less than 10. n%2 == 0 or n%3 == 0 is true if either of the conditions is true, that is, if the number is divisible by 2 or 3. Finally, the not operator negates a Boolean expression, so not(x > y) is true if x > y is false, that is, if x is less than or equal to y. Non-zero number is said to be true in Boolean expressions.

6. What is conditional execution?

The ability to check the condition and change the behavior of the program accordingly is called conditional execution. Example:

If statement:

The simplest form of if statement is:

Syntax:

if

statement:

Eg:

if x > 0:

print 'x is positive'

The boolean expression after ‘if’ is called the condition. If it is true, then the indented statement gets executed. If not, nothing happens.

7. What is alternative execution?

A second form of if statement is alternative execution, that is, if …else, where there are two possibilities and the condition determines which one to execute.

Eg:

if x%2 == 0:

print 'x is even'

else:

print 'x is odd'

8. What are chained conditionals?

Sometimes there are more than two possibilities and we need more than two branches. One way to express a computation like that is a chained conditional:

Eg:

if x < y:

print 'x is less than y'

elif x > y:

print 'x is greater than y'

else:

print 'x and y are equal'

elif is an abbreviation of “else if.” Again, exactly one branch will be executed. There is no limit on the number of elif statements. If there is an else clause, it has to be at the end, but there doesn’t have to be one.

9. Explain while loop with example. Eg:

def countdown(n):

while n > 0:

print n

n = n-1

print 'Blastoff!'

More formally, here is the flow of execution for a while statement:

1.    Evaluate the condition, yielding True or False.

2.    If the condition is false, exit the while statement and continue execution at the next statement.

3.    If the condition is true, execute the body and then go back to step 1

9. Explain ‘for loop’ with example.

The general form of a for statement is

Syntax:

for variable in sequence:

code block

Eg:

x = 4

for i in range(0, x):

print i

10. What is a break statement?

When a break statement is encountered inside a loop, the loop is immediately terminated and the program control resumes at the next statement following the loop.

Eg:

while True:

line = raw_input('>')

if line == 'done':

break

print line

print'Done!'

11. What is a continue statement?

The continue statement works somewhat like a break statement. Instead of forcing termination, it forces the next iteration of the loop to take place, skipping any code in between.

Eg:

for num in range(2,10):

if num%2==0;

print “Found an even number”, num

continue

print “Found a number”, num

12. Compare return value and composition. Return Value:

Return gives back or replies to the caller of the function. The return statement causes our function to exit and hand over back a value to its caller.

Eg:

def area(radius):

temp = math.pi * radius**2

return temp

Composition:

Calling one function from another is called composition.

Eg:

def circle_area(xc, yc, xp, yp):

radius = distance(xc, yc, xp, yp)

result = area(radius)

return result

13. What is recursion?

The process in which a function calls itself directly or indirectly is called recursion and the corresponding function is called as recursive function.

Eg:

def factorial(n):

if n == 1:

return 1

else:

return n * factorial(n-1)

14. Explain global and local scope.

The scope of a variable refers to the places that we can see or access a variable. If we define a variable on the top of the script or module, the variable is called global variable. The variables that are defined inside a class or function is called local variable.

Eg:

def my_local():

a=10

print(“This is local variable”)

Eg:

a=10

def my_global():

print(“This is global variable”)

15. Compare string and string slices.

A string is a sequence of character.

Eg: fruit = ‘banana’

String Slices :

A segment of a string is called string slice, selecting a slice is similar to selecting a character. Eg: >>> s ='Monty Python'

>>>     print s[0:5]

Monty

>>>     print s[6:12]

Python

16. Define string immutability.

Python strings are immutable. ‘a’ is not a string. It is a variable with string value. We can’t mutate the string but can change what value of the variable to a new string.

17. Mention a few string functions.

s.captilize() – Capitalizes first character of string

s.count(sub) – Count number of occurrences of sub in string

s.lower() – converts a string to lower case

s.split() – returns a list of words in string

18. What are string methods?

A method is similar to a function—it takes arguments and returns a value—but the syntax is different. For example, the method upper takes a string and returns a new string with all uppercase letters:

Instead of the function syntax upper(word), it uses the method syntax word.upper() .>>> >>>word = 'banana'

>>>     new_word = word.upper()

>>>     print new_word

BANANA

19. Explain about string module.

The string module contains number of useful constants and classes, as well as some deprecated legacy functions that are also available as methods on strings.

Eg:

20. What is the purpose of pass statement?

Using a pass statement is an explicit way of telling the interpreter to do nothing.

Eg:

def bar():

ass

If the function bar() is called, it does absolutely nothing.

Part A:

1.              What are Boolean values?

2.              Define operator and operand?

3.              Write the syntax for if with example?

4.              Write the syntax and flowchart for if else.

5.              Write the syntax and flowchart for chained if.

6.              define state

7.              Write the syntax for while loop with flowchart.

8.              Write the syntax for for loopwith flowchart.

9.              Differentiate break and continue.

10.        mention the use of pass

11.        what is fruitful function

12.        what is void function

13.        mention the different ways of writing return statement

14.        What is parameter and list down its type?

15.        What is local and global scope?

16.        Differentiate local and global variable?

17.        What is function composition, give an example?

18.        Define recursion.

19.        Differentiate iteration and recursion.

20.        Define string. How to get a string at run time.

21.        What is slicing? Give an example.

22.        What is immutability of string?

23.        List out some string built in function with example?

24.        Define string module?

25.        How can list act as array?

26.        write a program to check the number is odd or even.

27.        write a program to check the number positive or negative

28.        write a program to check the year is leap year or not

29.        write a program to find greatest of two numbers

30.        write a program for checking eligibility for vote

31.        write a program to find sum of n numbers

32.        write a program to find factorial of given numbers

33.        write a program to find sum of digits of a number

34.        Write a program to reverse the given number.

35.        Write a program to check the given number is palindrome or not.

36.        write a program to check the given number is Armstrong or not

37.        how can you use for loop in sequence.

38.        how can you use else statement if loops.

39.        What is the use of map() function?