Python Interview Questions

This page contains a list of typical Python Interview Questions and Answers.

Python Interview Questions

These questions and answers cover some fundamental Python concepts that are often discussed in interviews.

1) What is the difference between global and local scope?

• A variable created inside a function belongs to the local scope of that function, and can only be used inside that function.
• A variable created in the main body of the Python code is a global variable and belongs to the global scope. Global variables are available from within any scope, global and local.

2) What is an iterator in Python?

• An iterator is an object that contains a countable number of values.
• An iterator is an object that can be iterated upon, meaning that you can traverse through all the values.
• Technically, in Python, an iterator is an object which implements the iterator protocol, which consist of the methods __iter__() and __next__().

3) What is the __init__() function in Python?

• All classes in Python have a function called __init__(), which is always executed when the class is being initiated.
• We can use the __init__() function to assign values to object properties, or other operations that are necessary to do when the object is being created.

4) When should you use lambda functions in Python?

• Use lambda functions when an anonymous function is required for a short period of time.

5) What is the difference between lists, tuples and sets?

• Lists, tuples and sets are all used to store multiple items in a single variable.
• A list is a collection of data which is ordered and changeable (elements can be added, removed and changed).
• A tuple is a collection of data which is ordered and unchangeable (elements cannot be added, removed or changed).
• A set is a collection of data which is unordered, unchangeable, and unindexed.

6) How can you check if all the characters in a string are alphanumeric?

• You can use the isalnum() method, which returns True if all the characters are alphanumeric, meaning alphabet letter (a-z) and numbers (0-9).

7) How can you convert a string to an integer?

• You can use the int() function, like this:
num = "5"
convert = int(num)

8) What is indentation in Python, and why is it important?

• Indentation refers to the spaces at the beginning of a code line. Where in other programming languages the indentation in code is for readability only, the indentation in Python is very important.
• Python uses indentation to indicate a block of code.
• Python will give you an error if you skip the indentation.

9) What is the correct syntax to output the type of a variable or object in Python?

print(type(x))

10) Which collection does not allow duplicate members?

• SET

11) What is Inheritance in Python?

• Inheritance allows us to define a class that inherits all the methods and properties from another class.
• Parent class is the class being inherited from, also called base class.
• Child class is the class that inherits from another class, also called derived class.

12) What is the output of the following code?

x = 41

if x > 10:
  print("Above ten,")
  if x > 20:
    print("and also above 20!")
  else:
    print("but not above 20.")

• Above ten,
  and also above 20!

13) Can you list Python's primary built-in data types, in categories?

• Text Type: str
• Numeric Types: int, float, complex
• Sequence Types: list, tuple, range
• Mapping Type: dict
• Set Types: set, frozenset
• Boolean Type: bool
• Binary Types: bytes, bytearray, memoryview

14) What are Membership Operators?

• Membership operators are used to test if a sequence is present in an object. The in and not in operators are examples of these:

x = ["apple", "banana"]
print("banana" in x) # returns True

x = ["apple", "banana"]
print("pineapple" not in x) # returns True

15) Which statement can be used to avoid errors if an if statement has no content?

• The pass statement

16) What are Arbitrary Arguments?

• Arbitrary Arguments are often shortened to *args in Python documentations.
• If you do not know how many arguments that will be passed into your function, add a * before the parameter name in the function definition. This way the function will receive a tuple of arguments, and can access the items accordingly.

17) How can you create and use a Module in Python??

• To create a module just save the code you want in a file with the file extension .py:

  def greeting(name):
    print("Hello, " + name)

• Now we can use the module we just created, by using the import statement:

  import mymodule
  
  mymodule.greeting("Jonathan")

18) Can you copy a List in Python by simply writing: list2 = list1?

• No, because: list2 will only be a reference to list1, and changes made in list1 will automatically also be made in list2.
• To make a copy of a list, you can use copy() or the list() method.

19) How can you return a range of characters of a string?

• You can return a range of characters by using the "slice syntax".
• Specify the start index and the end index, separated by a colon, to return a part of the string, for example:

Get the characters from position 2 to position 5 (not included):

b = "Hello, World!"
print(b[2:5])

20) What is a class in Python, and how do you use it?

• A Class is like an object constructor, or a "blueprint" for creating objects.
• You can create a class with the class keyword:
  class MyClass:
  x = 5

  Now we can use the class named MyClass to create objects:

  Create an object named p1, and print the value of x:

  p1 = MyClass()
  print(p1.x)