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34. What will be the output produced on execution of the following code?
>>> name = "Computer Science with Python"
>>> print(name[9:17])
Ans. Science
35. What are the built-in types that Python provides?
Ans. Python provides built-in types of two types: mutable and immutable. Mutable types:
• List
• Sets
• Dictionaries
Immutable built-in types:
• Strings
• Tuples
• Numbers
36. Evaluate the following expressions:
a. 6 * 3 + 4**2 // 5 – 8
b. 10 > 5 and 7 > 12 or not 18 > 3
Ans. a. 13
b. False
37. What do you understand by the term iteration?
Ans. Repetition of statement/s finite number of times is known as iteration.
38. What is the use of // operator in Python?
Ans. It is a divide and truncate the quotient operator; for example, 15//4 -->3, 15//4.0 -->
3.0, 15.0//4.0 --> 3.0. Note that if one (both) of the operands is (are) floating point numbers, it yields a floating
point number.
39. What are literals in Python?
Ans. A literal is a fixed value, examples include string literals, numeric literals, and boolean literals.
40. What is a Dictionary in Python?
Ans. Dictionary is an important built-in data type in Python. It defines one-to-one relationship between keys and
values. Dictionaries contain a pair of keys and their corresponding values.
Dictionaries are indexed by keys.
41. How will you reverse a list?
Ans. list.reverse() − Reverses items of list in place.
42. Differentiate between a candidate key and a primary key for a relation in SQL.
Ans. A candidate key is any column or combination of columns that could be used as a primary key, whereas a primary
key is the chosen candidate key that uniquely identifies rows and enforces entity integrity in the table.
43. What is meant by a NULL value? What are the reasons that lead to their occurrence in database relations?
Ans. The absence of a data item is represented by a special value called the null value. There are three situations
which may require the use of null values
i. When a particular attribute does not apply to an entity,
ii. Value of an attribute is unknown, although it exists;
iii. When the value is unknown because it does not exist
Viva Voce Questions 351

