Python Developer Interview Preparation Guide

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☛ List Vs Tuple.
The major difference between a list and the tuple is that the list is mutable while tuple is not. A tuple is allowed to be hashed, for example, using it as a key for dictionaries.

The ternary operator is an alternative for the conditional statements. It combines of the true or false values with a statement that you need to test. The syntax would look like the one given below.

[onTrue] if [Condition] else [onFalse]

x, y = 35, 75
smaller = x if x < y else y
print(smaller)

The <yield> keyword can turn any function into a generator. It works like a standard return keyword. But it’ll always return a generator object. Also, a function can have multiple calls to the <yield> keyword.

See the example below.

def testgen(index):
weekdays = ['sun','mon','tue','wed','thu','fri','sat']
yield weekdays[index]
yield weekdays[index+1]

day = testgen(0)
print next(day), next(day)

#output: sun mon

PEP 8 is a coding convention, a set of recommendation, about how to write your Python code more readable.

There are mutable and Immutable types of Pythons built in types Mutable built-in types
☛ List
☛ Sets
☛ Dictionaries

Immutable built-in types
☛ Strings
☛ Tuples
☛ Numbers

A mechanism to select a range of items from sequence types like list, tuple, strings etc. is known as slicing.

To share global variables across modules within a single program, create a special module. Import the config module in all modules of your application. The module will be available as a global variable across modules.

It is a Floor Divisionoperator , which is used for dividing two operands with the result as quotient showing only digits before the decimal point. For instance, 10//5 = 2 and 10.0//5.0 = 2.0.

The common way for the flask script to work is

☛ Either it should be the import path for your application
☛ Or the path to a Python file

Dogpile effect is referred to the event when cache expires, and websites are hit by the multiple requests made by the client at the same time. This effect can be prevented by using semaphore lock. In this system when value expires, first process acquires the lock and starts generating new value.

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.

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.

Python is one of the most successful interpreted languages. When you write a Python script, it doesn’t need to get compiled before execution. Few other interpreted languages are PHP and Javascript.

☛ Benefits Of Python Programming.
Python is a dynamic-typed language, this means that you don’t need to mention the date type of variables during their declaration. It allows to set variables like var1=101 and var2 =” You are an engineer.” without any error.
Python supports object orientated programming as you can define classes along with the composition and inheritance. It doesn’t use access specifiers like public or private).
Functions in Python are like first-class objects. It suggests you can assign them to variables, return from other methods and pass as arguments.
Developing using Python is quick but running it is often slower than compiled languages. Luckily, Python enables to include the “C” language extensions so you can optimize your scripts.
Python has several usages like web-based applications, test automation, data modeling, big data analytics and much more. Alternatively, you can utilize it as “glue” layer to work with other languages.

☛ PEP 8.
PEP 8 is the latest Python coding standard, a set of coding recommendations. It guides to deliver more readable Python code.

☛ You can use PyChecker, which is a static analyzer. It identifies the bugs in Python project and also reveals the style and complexity related bugs.
☛ Another tool is Pylint, which checks whether the Python module satisfies the coding standard.

No, Python does not have a Switch statement, but you can write a Switch function and then use it.

There are two ways to copy objects in Python.

☛ copy.copy() function
☛ It makes a copy of the file from source to destination.
☛ It’ll return a shallow copy of the parameter.
☛ copy.deepcopy() function
☛ It also produces the copy of an object from the source to destination.
☛ It’ll return a deep copy of the parameter that you can pass to the function.

NumPy is a Python package for scientific computing which can deal with large data sizes. It includes a powerful N-dimensional array object and a set of advanced functions.

Also, the NumPy arrays are superior to the built-in lists. There are a no. of reasons for this.

☛ NumPy arrays are more compact than lists.
☛ Reading and writing items is faster with NumPy.
☛ Using NumPy is more convenient than to the standard list.
☛ NumPy arrays are more efficient as they augment the functionality of lists in Python.

It is a single expression anonymous function often used as inline function.

Python sequences can be index in positive and negative numbers. For positive index, 0 is the first index, 1 is the second index and so forth. For negative index, (-1) is the last index and (-2) is the second last index and so forth.

To generate random numbers in Python, you need to import command as

import random

random.random()

This returns a random floating point number in the range [0,1)

The data in the failed server won’t get removed, but there is a provision for auto-failure, which you can configure for multiple nodes. Fail-over can be triggered during any kind of socket or Memcached server level errors and not during normal client errors like adding an existing key, etc.

☛ Python has a multi-threading package but if you want to multi-thread to speed your code up.
☛ 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.

Flask is a web micro framework for Python based on “Werkzeug, Jinja2 and good intentions” BSD license. Werkzeug and Jinja2 are two of its dependencies. This means it will have little to no dependencies on external libraries. It makes the framework light while there is little dependency to update and less 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. The user can modify the session if only it has the secret key Flask.secret_key.

The pass statement is a null operation. Nothing happens when it executes. You should use “pass” keyword in lowercase. If you write “Pass” you’ll face an error like “NameError: name Pass is not defined.” Python statements are case sensitive.

letter = "hai friend"
for i in letter:
if i == "a":
pass
print("pass statement is execute ..............")
else:
print(i)

☛ Lambda Vs Def.
def can hold multiple expressions while lambda is a uni-expression function.
def generates a function and designates a name so as to call it later. lambda forms a function and returns the function itself.
def can have a return statement. lambda can’t have return statements
lambda supports to get used inside a list and dictionary.