1) What is Python? What are the benefits of using Python?
Python is a programming language with objects, modules, threads, exceptions and automatic memory management. The benefits of pythons are that it is simple and easy, portable, extensible, build-in data structure and it is an open source.
2) What is PEP 8?
PEP 8 is a coding convention, a set of recommendation, about how to write your Python code more readable.
3) What is pickling and unpickling?
Pickle module accepts any Python object and converts it into a string representation and dumps it into a file by using dump function, this process is called pickling. While the process of retrieving original Python objects from the stored string representation is called unpickling.
4) How Python is interpreted?
Python language is an interpreted language. Python program runs directly from the source code. It converts the source code that is written by the programmer into an intermediate language, which is again translated into machine language that has to be executed.
5) How memory is managed in Python?
- Python memory is managed by Python private heap space. All Python objects and data structures are located in a private heap. The programmer does not have an access to this private heap and interpreter takes care of this Python private heap.
- The allocation of Python heap space for Python objects is done by Python memory manager. The core API gives access to some tools for the programmer to code.
- Python also have an inbuilt garbage collector, which recycle all the unused memory and frees the memory and makes it available to the heap space.
6) What are the tools that help to find bugs or perform static analysis?
PyChecker is a static analysis tool that detects the bugs in Python source code and warns about the style and complexity of the bug. Pylint is another tool that verifies whether the module meets the coding standard.
7) What are Python decorators?
A Python decorator is a specific change that we make in Python syntax to alter functions easily.
8) What is the difference between list and tuple?
The difference between list and tuple is that list is mutable while tuple is not. Tuple can be hashed for e.g as a key for dictionaries.
9) How are arguments passed by value or by reference?
Everything in Python is an object and all variables hold references to the objects. The references values are according to the functions; as a result you cannot change the value of the references. However, you can change the objects if it is mutable.
10) What is Dict and List comprehensions are?
They are syntax constructions to ease the creation of a Dictionary or List based on existing iterable.
11) Is Python fully object oriented?
Python does follow an object-oriented programming paradigm and has all the basic OOPs concepts such as inheritance, polymorphism, and more, with the exception of access specifiers. Python doesn’t support strong encapsulation (adding a private keyword before data members). Although, it has a convention that can be used for data hiding, i.e., prefixing a data member with two underscores.
12) What is lambda function in Python?
A lambda function is an anonymous function (a function that does not have a name) in Python. To define anonymous functions, we use the ‘lambda’ keyword instead of the ‘def’ keyword, hence the name ‘lambda function’. Lambda functions can have any number of arguments but only one statement.
13) What is self-keyword in Python?
Self-keyword is used as the first parameter of a function inside a class that represents the instance of the class. The object or the instance of the class is automatically passed to the method that it belongs to and is received in the ‘self-keyword.’ Users can use another name for the first parameter of the function that catches the object of the class, but it is recommended to use ‘self-keyword’ as it is more of a Python convention.
14) What are control flow statements in Python?
Control flow statements are used to manipulate or change the execution flow of a program. Generally, the flow of the execution of a program runs from top to bottom, but certain statements (control flow statements) in Python can break this top-to-bottom order of execution. Control flow statements include decision-making, looping, and more.
15) What is the difference between append() and extend() methods?
Both append() and extend() methods are methods used to add elements at the end of a list.
- append(element): Adds the given element at the end of the list that called this append() method
- extend(another-list): Adds the elements of another list at the end of the list that called this extend() method.
16) What are loop interruption statements in Python?
There are two types of loop interruption statements in Python that let users terminate a loop iteration prematurely, i.e., not letting the loop run its full iterations.
Following are the two types of loop interruption statements:
- Python break statement: This statement immediately terminates the loop entirely, and the control flow of the program is shifted directly to the outside of the loop.
- Python continue statement: Continue statement terminates the current loop iteration and moves the control flow of the program to the next iteration of the loop, letting the user skip only the current iteration.
17). What is docstring in Python?
Python lets users include a description (or quick notes) for their methods using documentation strings or docstrings. Docstrings are different from regular comments in Python as, rather than being completely ignored by the Python Interpreter like in the case of comments, Python documentation strings can actually be accessed at the run time using the dot operator when docstring is the first statement in a method or function.
18) How is memory managed in Python?
- Memory management in python is managed by Python private heap space. All Python objects and data structures are located in a private heap. The programmer does not have access to this private heap. The python interpreter takes care of this instead.
- The allocation of heap space for Python objects is done by Python’s memory manager. The core API gives access to some tools for the programmer to code.
- Python also has an inbuilt garbage collector, which recycles all the unused memory and so that it can be made available to the heap space.
19) What is namespace in Python?
A namespace is a naming system used to make sure that names are unique to avoid naming conflicts.
20) What is PYTHONPATH?
It is an environment variable which 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.
21) 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
22) What are local variables and global variables in Python?
Global Variables:
Variables declared outside a function or in 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.
When you try to access the local variable outside the function add(), it will throw an error.
23. Is python case sensitive?
Yes. Python is a case sensitive language.
24 What is type conversion in Python?
Type conversion refers to the conversion of one data type iinto another.
int() – converts any data type into integer type
float() – converts any data type into float type
ord() – converts characters into integer
hex() – converts integers to hexadecimal
oct() – converts integer to octal
tuple() – This function is used to convert to a tuple.
set() – This function returns the type after converting to set.
list() – This function is used to convert any data type to a list type.
dict() – This function is used to convert a tuple of order (key,value) into a dictionary.
str() – Used to convert integer into a string.
complex(real,imag) – This functionconverts real numbers to complex(real,imag) number.
25) How to install Python on Windows and set path variable?
To install Python on Windows, follow the below steps:
- Install python from this link: https://www.python.org/downloads/
- After this, install it on your PC. Look for the location where PYTHON has been installed on your PC using the following command on your command prompt: cmd python.
- Then go to advanced system settings and add a new variable and name it as PYTHON_NAME and paste the copied path.
- Look for the path variable, select its value and select ‘edit’.
- Add a semicolon towards the end of the value if it’s not present and then type %PYTHON_HOME%
26) 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.
27) What is the difference between Python Arrays and lists?
Arrays and lists, in Python, have the same way of storing data. But, arrays can hold only a single data type elements whereas lists can hold any data type elements.
28) 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.
29) What are python iterators?
Ans: Iterators are objects which can be traversed though or iterated upon.
30) How can you generate random numbers in Python?
Random module is the standard module that is used to generate a random number. The
is defined as:
import random
random.random
The statement random.random() method return the floating point number that is in the range of [0, 1). The function generates random float numbers. The methods that are used with the random class are the bound methods of the hidden instances. The instances of the Random can be done to show the multi-threading programs that creates a different instance of individual threads. The other random generators that are used in this are:
- randrange(a, b): it chooses an integer and define the range in-between [a, b). It returns the elements by selecting it randomly from the range that is specified. It doesn’t build a range object.
- uniform(a, b): it chooses a floating point number that is defined in the range of [a,b).Iyt returns the floating point number
- normalvariate(mean, sdev): it is used for the normal distribution where the mu is a mean and the sdev is a sigma that is used for standard deviation.
- The Random class that is used and instantiated creates an independent multiple random number generators.
31) 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 like 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 really memory sensitive system such as a cell phone that you are working with, as 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.
32) 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 #
33) What is pickling and unpickling?
Pickle module accepts any Python object and converts it into a string representation and dumps it into a file by using dump function, this process is called pickling. While the process of retrieving original Python objects from the stored string representation is called unpickling
34) What are the generators in python?
Functions that return an iterable set of items are called generators.
35) How will you capitalize the first letter of string?
In Python, the capitalize() method capitalizes the first letter of a string. If the string already consists of a capital letter at the beginning, then, it returns the original string.
36) How to comment multiple lines in python?
Multi-line comments appear in more than one line. All the lines to be commented are to be prefixed by a #. You can also a very good shortcut method to comment multiple lines. All you need to do is hold the ctrl key and left click in every place wherever you want to include a # character and type a # just once. This will comment all the lines where you introduced your cursor.
37) What are docstrings in Python?
Docstrings are not actually comments, but, they are documentation strings. These docstrings are within triple quotes. They are not assigned to any variable and therefore, at times, serve the purpose of comments as well.
38) 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
39) What is the usage of help() and dir() function in Python?
Help() and dir() both functions are accessible from the Python interpreter and used for viewing a consolidated dump of built-in functions.
- Help() function: The help() function is used to display the documentation string and also facilitates you to see the help related to modules, keywords, attributes, etc.
- Dir() function: The dir() function is used to display the defined symbols.
40) 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.
40 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.
41) How can the ternary operators be used in python?
The Ternary operator is the operator that is used to show the conditional statements. This consists of the true or false values with a statement that has to be evaluated for it.
Syntax:
The Ternary operator will be given as:
[on_true] if [expression] else [on_false]x, y = 25, 50big = x if x < y else y
Example:
The expression gets evaluated like if x<y else y, in this case if x<y is true then the value is returned as big=x and if it is incorrect then big=y will be sent as a result.
42) 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.
43). Explain split(), sub(), subn() methods of “re” module in Python.
To modify the strings, Python’s “re” module is providing 3 methods. They are:
- split() – uses a regex pattern to “split” a given string into a list.
- sub() – finds all substrings where the regex pattern matches and then replace them with a different string
- subn() – it is similar to sub() and also returns the new string along with the no. of replacements.
44) What are Python packages?
Python packages are namespaces containing multiple modules.
45) 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.
46) What are the built-in types of python?
Built-in types in Python are as follows –
- Integers
- Floating-point
- Complex numbers
- Strings
- Boolean
- Built-in functions
47) How to add values to a python array?
Elements can be added to an array using the append(), extend() and the insert (i,x) functions.
48) 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.
49) 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.
50) 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.