DridhOn

Most Consistently Asked in Top IT Company Interview

1. What are the key features of Python?

  • Python is an interpreted language. That means that, unlike languages like C and its variants, Python does not need to be compiled before it is run. Other interpreted languages include PHP, Perl, R-Programming, and Ruby.

    Python is dynamically typed, this means that you don’t need to state the types of variables when you declare them or anything like that. You can do things like a=10 and then b=”I’m from dridhOn” without error

    Python is well suited to object orientated programming in that it allows the definition of classes along with composition and inheritance. Python does not have access specifiers (like C or C++’s public, private).

    In Python, functions are first-class objects. This means that they can be assigned to variables, returned from other functions and passed into functions. Classes are also first class objects

2. Python is an interpreted language or compiler language. Explain.

  • No, Python is not a compiler language. Python is an interpreted language that is any programming language that is not in machine-level code before runtime. Therefore, Python is an interpreted language

3. What type of language is Python? Programming or scripting?

  • Python is capable of scripting, but in the general sense, it is considered a general-purpose programming language. Basically, all scripting languages are programming languages. The theoretical difference between the two is that scripting languages do not require the compilation step and are rather interpreted. Some scripting languages traditionally used without an explicit compilation step are JavaScript, PHP, Python, VBScript.

4. Difference between PEP and PIP?

  • PEP stands for Python Enhancement Proposal. It is a set of rules that specify how to format Python code for maximum readability.
  • While this PEP only proposes documentation changes for Python 2.7, once pip has a Windows installer available, a separate PEP will be created and submitted proposing the creation and distribution of aggregate installers for future CPython 2.7 maintenance releases that combine the CPython, pip, and Python Launcher for Windows installers into a single download (the separate downloads would still remain available – the aggregate installers would be provided as a convenience, and as a clear indication of the recommended operating environment for Python in Windows systems).

5. What is the difference between list and tuples in Python?

  • LIST vs TUPLES

    LIST                                                                             TUPLES

    Lists are mutable i.e they can be edited.          Tuples are immutable (tuples are lists that can’t be edited).

    Lists are slower than tuples.                                 Tuples are faster than the list.

    Syntax: list_1 = [10, ‘Chelsea’, 20]                           Syntax: tup_1 = (10, ‘Chelsea’ , 20)

6. What is PYTHONPATH?

  • It is an environment variable that is used when a module is imported. Whenever a module is imported, PYTHONPATH is also looked up to check for the presence of the imported modules in various directories. The interpreter uses it to determine which module to load.

7. What are python modules? Name some commonly used built-in modules in Python?

  • Python modules are files containing Python code. This code can either be functions classes or variables. A Python module is a .py file containing executable code. Some of the commonly used built-in modules are:
  • os
  • sys
  • math
  • random
  • data time
  • JSON

8. What are local variables and global variables in Python?

  • Global Variables: Variables declared outside a function or in a global space are called global variables. These variables can be accessed by any function in the program.

  • Local Variables: Any variable declared inside a function is known as a local variable. This variable is present in the local space and not in the global space.

9. Is indentation required in Python?

  • Indentation is necessary for Python. It specifies a block of code. All code within loops, classes, functions, etc is specified within an indented block. It is usually done using four space characters. If your code is not indented necessarily, it will not execute accurately and will throw errors as well.

10. What is __init__?

  • __init__ is a method or constructor in Python. This method is automatically called to allocate memory when a new object/ instance of a class is created. All classes have the __init__ method.

11. What is a lambda function?

  • An anonymous function is known as a lambda function. This function can have any number of parameters but can have just one statement.
  • Example:
  • a = lambda x,y : x+y
  • print(a(5, 6)
  • Output: 11

12. What is self in Python?

  • Self is an instance or an object of a class. In Python, this is explicitly included as the first parameter. However, this is not the case in Java where it’s optional.  It helps to differentiate between the methods and attributes of a class with local variables.

  • The self variable in the init method refers to the newly created object while in other methods, it refers to the object whose method was called.

13. How does break, continue and pass work?

  • Break: Allows loop termination when some condition is met and the control is transferred to the next statement.
  • Continue: Allows skipping some part of a loop when some specific condition is met and the control is transferred to the beginning of the loop
  • Pass: Used when you need some block of code syntactically, but you want to skip its execution. This is basically a null operation. Nothing happens when this is executed.

14. What is the difference between range & xrange?

  • For the most part, xrange and range are the exact same in terms of functionality. They both provide a way to generate a list of integers for you to use, however you please. The only difference is that range returns a Python list object and x range returns an xrange object.
  • This means that xrange doesn’t actually generate a static list at run-time as range does. It creates the values as you need them with a special technique called yielding. This technique is used with a type of object known as generators. That means that if you have a really gigantic range you’d like to generate a list for, say one billion, xrange is the function to use.
  • This is especially true if you have a real memory-sensitive system such as a cell phone that you are working with, as the range will use as much memory as it can to create your array of integers, which can result in a Memory Error and crash your program. It’s a memory-hungry beast.

15. How do you write comments in Python?

  • Comments in Python start with a # character. However, alternatively at times, commenting is done using docstrings (strings enclosed within triple quotes).

  • Example:

    #Comments in Python start like this

    print(“Comments in Python start with a #”)

    Output:  Comments in Python start with a #

16. What is the purpose of is, not and in operators?

  • Operators are special functions. They take one or more values and produce a corresponding result.

    is: returns true when 2 operands are true (Example: “a” is ‘a’)

    not: returns the inverse of the Boolean value

    in: checks if some element is present in some sequence

17. Whenever Python exits, why isn’t all the memory de-allocated?

  • Whenever Python exits, especially those Python modules which are having circular references to other objects or the objects that are referenced from the global namespaces are not always de-allocated or freed. It is impossible to de-allocate those portions of memory that are reserved by the C library. On exit, because of having its own efficient clean-up mechanism, Python would try to de-allocate/destroy every other object.

18. What is a dictionary in Python?

  • The built-in datatypes in Python is called dictionary. It defines one-to-one relationship between keys and values. Dictionaries contain pair of keys and their corresponding values. Dictionaries are indexed by keys.

19. How can the ternary operators be used in python?

  • The Ternary operator is the operator that is used to show conditional statements. This consists of the true or false values with a statement that has to be evaluated for it.

20. What does this mean: *args, **kwargs? And why would we use it?

  • We use *args when we aren’t sure how many arguments are going to be passed to a function, or if we want to pass a stored list or tuple of arguments to a function. **kwargs is used when we don’t know how many keyword arguments will be passed to a function, or it can be used to pass the values of a dictionary as keyword arguments. The identifiers args and kwargs are a convention, you could also use *bob and **billy but that would not be wise.

21. What are negative indexes and why are they used?

  • The sequences in Python are indexed and it consists of the positive as well as negative numbers. The numbers that are positive use ‘0’ that is used as the first index and ‘1’ as the second index and the process goes on like that.

  • The index for the negative number starts from ‘-1’ that represents the last index in the sequence and ‘-2’ is the penultimate index and the sequence carries forward like the positive number.

  • The negative index is used to remove any new-line spaces from the string and allow the string to accept the last character that is given as S[:-1]. The negative index is also used to show the index to represent the string in the correct order.

     

22. What are Python packages?

  • Python packages are namespaces containing multiple modules.

23. How can files be deleted in Python?

  • To delete a file in Python, you need to import the OS Module. After that, you need to use the os.remove() function.

24. How to add values to a Python List?

  • Elements can be added to an array using the append(), extend() and the insert (i,x) functions.

25. How to remove values to a Python array?

  • Array elements can be removed using pop() or remove() method. The difference between these two functions is that the former returns the deleted value whereas the latter does not.

26. Does Python have Oops concepts?

  • Python is an object-oriented programming language. This means that any program can be solved in python by creating an object model. However, Python can be treated as procedural as well as structural language.

27. What is the difference between deep and shallow copy?

  • Shallow copy is used when a new instance type gets created and it keeps the values that are copied in the new instance. Shallow copy is used to copy the reference pointers just like it copies the values. These references point to the original objects and the changes made in any member of the class will also affect the original copy of it. Shallow copy allows faster execution of the program and it depends on the size of the data that is used.

  • Deep copy is used to store the values that are already copied. Deep copy doesn’t copy the reference pointers to the objects. It makes the reference to an object and the new object that is pointed by some other object gets stored. The changes made in the original copy won’t affect any other copy that uses the object. Deep copy makes execution of the program slower due to making certain copies for each object that is been called.

28. How is Multithreading achieved in Python?

  • Python has a multi-threading package but if you want to multi-thread to speed your code up, then it’s usually not a good idea to use it.
  • Python has a construct called the Global Interpreter Lock (GIL). The GIL makes sure that only one of your ‘threads’ can execute at any one time. A thread acquires the GIL, does a little work, then passes the GIL onto the next thread.
  • This happens very quickly so to the human eye it may seem like your threads are executing in parallel, but they are really just taking turns using the same CPU core.
  • All this GIL passing adds overhead to execution. This means that if you want to make your code run faster then using the threading package often isn’t a good idea.

29. What are Python libraries? Name a few of them.

  • Python libraries are a collection of Python packages. Some of the majorly used python libraries are – Numpy, Pandas, Matplotlib, Scikit-learn and many more.

30. Does python support multiple inheritance?

  • Multiple inheritances mean that a class can be derived from more than one parent class. Python does support multiple inheritances, unlike Java.

31. What is Polymorphism in Python?

  • Polymorphism means the ability to take multiple forms. So, for instance, if the parent class has a method named ABC then the child class also can have a method with the same name ABC having its own parameters and variables. Python allows polymorphism.

32. Define encapsulation in Python?

  • Encapsulation means binding the code and the data together. A Python class in an example of encapsulation.

33. How to create an empty class in Python?

  • An empty class is a class that does not have any code defined within its block. It can be created using the pass keyword. However, you can create objects of this class outside the class itself. IN PYTHON THE PASS command does nothing when its executed. it’s a null statement.

34. What does an object() do?

  • It returns a featureless object that is a base for all classes. Also, it does not take any parameters.

35. Write a program in Python to produce Star triangle.

  • def pyfunc(r):

        for x in range(r):

            print(‘ ‘*(r-x-1)+’*’*(2*x+1))   

    pyfunc(3)

    Output:

     

            *

           ***

          *****

36. Write a sorting algorithm for a numerical dataset in Python.

  • The following code can be used to sort a list in Python:

  • list = [“1”, “4”, “0”, “6”, “9”]

    list = [int(i) for i in list]

    list.sort()

    print (list)

37. Explain what Flask is and its benefits?

  • Flask is a web microframework for Python based on “Werkzeug, Jinja2 and good intentions” BSD license. Werkzeug and Jinja2 are two of their dependencies. This means it will have little to no dependencies on external libraries.  It makes the framework light while there is a little dependency to update and fewer security bugs.

  • A session basically allows you to remember information from one request to another. In a flask, a session uses a signed cookie so the user can look at the session contents and modify them. The user can modify the session if only it has the secret key Flask.secret_key.

38. Is Django better than Flask?

  • Django and Flask map the URLs or addresses typed in the web browsers to functions in Python.

    Flask is much simpler compared to Django but, Flask does not do a lot for you meaning you will need to specify the details, whereas Django does a lot for you wherein you would not need to do much work. Django consists of prewritten code, which the user will need to analyze whereas Flask gives the users to create their own code, therefore, making it simpler to understand the code. Technically both are equally good and both contain their own pros and cons.

39. Mention the differences between Django, Pyramid and Flask.

  • Flask is a “microframework” primarily build for a small application with simpler requirements. In a flask, you have to use external libraries. Flask is ready to use.

  • Pyramid is built for larger applications. It provides flexibility and lets the developer use the right tools for their project. The developer can choose the database, URL structure, templating style, and more. The pyramid is heavily configurable.

  • Django can also be used for larger applications just like Pyramid. It includes an ORM.

40. Mention the differences between Django, Pyramid and Flask.

  • Flask is a “microframework” primarily build for a small application with simpler requirements. In a flask, you have to use external libraries. Flask is ready to use.

  • Pyramid is built for larger applications. It provides flexibility and lets the developer use the right tools for their project. The developer can choose the database, URL structure, templating style, and more. The pyramid is heavily configurable.

  • Django can also be used for larger applications just like Pyramid. It includes an ORM.

41. Discuss Django architecture.

  • Django MVT Pattern:

    The developer provides the Model, the view, and the template then just maps it to a URL and Django does the magic to serve it to the user.

42. Explain how you can set up the Database in Django.

  • You can use the command edit mysite/setting.py, it is a normal python module with module-level representing Django settings.

    Django uses SQLite by default; it is easy for Django users as such it won’t require any other type of installation. In the case, your database choice is different that you have to the following keys in the DATABASE ‘default’ item to match your database connection settings.

    Engines: you can change the database by using ‘django.db.backends.sqlite3’ , ‘django.db.backeneds.mysql’, ‘django.db.backends.postgresql_psycopg2’, ‘django.db.backends.oracle’ and so on

    Name The name of your database. In the case if you are using SQLite as your database, in that case, the database will be a file on your computer, Name should be a full absolute path, including the file name of that file.

    If you are not choosing SQLite as your database then settings like Password, Host, User, etc. must be added.

    Django uses SQLite as a default database, it stores data as a single file in the filesystem. If you do have a database server—PostgreSQL, MySQL, Oracle, MSSQL—and want to use it rather than SQLite, then use your database’s administration tools to create a new database for your Django project. Either way, with your (empty) database in place, all that remains is to tell Django how to use it. This is where your project’s settings.py file comes in.

    We will add the following lines of code to the setting.py file:

    DATABASES = {

         ‘default’: {

              ‘ENGINE’ : ‘django.db.backends.sqlite3’,

              ‘NAME’ : os.path.join(BASE_DIR, ‘db.sqlite3’),

         }

    }

43. Give an example how you can write a VIEW in Django?

  • This is how we can use write a view in Django:

    from Django.http import HttpResponse

    import datetime

    def Current_datetime(request):

         now = datetime.datetime.now()

         html = “<html><body>It is now %s</body></html> % now

         return HttpResponse(html)

    Returns the current date and time, as an HTML document

43. Mention what the Django templates consist of.

  • The template is a simple text file.  It can create any text-based format like XML, CSV, HTML, etc.  A template contains variables that get replaced with values when the template is evaluated and tags (% tag %) that control the logic of the template.

44. Explain the use of session in Django framework?

  • Django provides a session that lets you store and retrieve data on a per-site-visitor basis. Django abstracts the process of sending and receiving cookies, by placing a session ID cookie on the client-side and storing all the related data on the server-side. So the data itself is not stored client-side. This is nice from a security perspective.

45. List out the inheritance styles in Django.

  • In Django, there are three possible inheritance styles:

    Abstract Base Classes: This style is used when you only want the parent’s class to hold information that you don’t want to type out for each child model.

    Multi-table Inheritance: This style is used If you are sub-classing an existing model and need each model to have its own database table.

    Proxy models: You can use this model, If you only want to modify the Python level behavior of the model, without changing the model’s fields.

46. How To Save An Image Locally Using Python Whose URL Address I Already Know?

  • We will use the following code to save an image locally from an URL address

    import urllib.request

    urllib.request.urlretrieve(“URL”, “local-filename.jpg”)

    Q83. How can you Get the Google cache age of any URL or web page?

    Ans: Use the following URL format:

    http://webcache.googleusercontent.com/search?q=cache:URLGOESHERE

    Be sure to replace “URLGOESHERE” with the proper web address of the page or site whose cache you want to retrieve and see the time for. For example, to check the Google Web cache age of dridhon.com you’d use the following URL:

47. How To Save An Image Locally Using Python Whose URL Address I Already Know?

  • We will use the following code to save an image locally from an URL address

    import urllib.request

    urllib.request.urlretrieve(“URL”, “local-filename.jpg”)

    Q83. How can you Get the Google cache age of any URL or web page?

    Ans: Use the following URL format:

    http://webcache.googleusercontent.com/search?q=cache:URLGOESHERE

    Be sure to replace “URLGOESHERE” with the proper web address of the page or site whose cache you want to retrieve and see the time for. For example, to check the Google Web cache age of dridhon.com you’d use the following URL:

48. What is map function in Python?

  • Map function executes the function given as the first argument on all the elements of the iterable given as the second argument. If the function given takes in more than 1 argument, then many tables are given. #Follow the link to know more similar functions.

49. What is the difference between NumPy and SciPy?

  • In an ideal world, NumPy would contain nothing but the array data type and the most basic operations: indexing, sorting, reshaping, basic elementwise functions, et cetera.

    All numerical code would reside in SciPy. However, one of NumPy’s important goals is compatibility, so NumPy tries to retain all features supported by either of its predecessors.

    Thus NumPy contains some linear algebra functions, even though these more properly belong in SciPy. In any case, SciPy contains more fully-featured versions of the linear algebra modules, as well as many other numerical algorithms.

    If you are doing scientific computing with python, you should probably install both NumPy and SciPy. Most new features belong in SciPy rather than NumPy.

50. How do you make 3D plots/visualizations using NumPy/SciPy?

  • Like 2D plotting, 3D graphics is beyond the scope of NumPy and SciPy, but just as in the 2D case, packages exist that integrate with NumPy. Matplotlib provides basic 3D plotting in the mplot3d subpackage, whereas Mayavi provides a wide range of high-quality 3D visualization features, utilizing the powerful VTK engine.

Play Video

Drop Us a query

Scroll to Top