The ultimate guide to senior engineering interviews. Strategies developed by FAANG engineers on Python concurrency, multithreading, monitors, and event loops. Prep faster for top company questions.

Concurrency in Python is one of the most complex and advanced topics brought up during senior engineering interviews. Knowledge of concurrency and multithreading can put interviewees at a considerable advantage. This course lays the foundations of advanced concurrency and multithreading and explains concepts such as Monitors, Event Loops and Deferred Callbacks in depth. It also builds simple and complete solutions to popular concurrency problems that can be asked about in interviews like the Reader-Writer Problem and the Dining Philosopher Problem. While prior knowledge of concurrency is not required to follow through with this course, familiarity with the very basic Python would be helpful.

Python Concurrency for Senior Engineering Interviews

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   # Program vs Process vs Thread   
   <div class="ans">
## Program
<p><span class="hi-yl">A program is a set of instructions and associated data that resides on the disk and is loaded by the operating system to perform a task.</span> An executable file or a python script file are examples of programs. In order to run a program, the operating system's kernel is first asked to <span class="hi-yl">create a new process, which is an environment in which a program is executed.</span></p>

## Process
<p><span class="hi-yl">A process is a program in execution</span>. A process is an execution environment that consists of instructions, user-data, and system-data segments, as well as lots of other resources such as CPU, memory, address-space, disk and network I/O acquired at runtime. A program can have several copies of it running at the same time but a process necessarily belongs to only one program.</p>

## Thread
<p><span class="hi-yl">A thread is the smallest unit of execution in a process</span> which simply executes instructions serially. A process can have multiple threads running as part of it. Usually, there would be some state associated with the process that is shared among all the threads and in turn each thread would have some state private to itself.</p> 
<p>The globally shared state amongst the threads of a process is visible and accessible to all the threads, and special attention needs to be paid when any thread tries to read or write to this global shared state. There are several constructs offered by various programming languages to guard and discipline the access to this global state, which we will go into further detail in upcoming lessons.</p>

## Notes
<p><span class="hi-yl">Note that a "program" and a "process" are often used interchangeably, though most of the time the intent is to refer to a process.</span></p>

<p>There's also the concept of "multiprocessing" systems, where multiple processes get scheduled on more than one CPU. Usually, this requires hardware support, where a single system comes with multiple cores or the execution takes place in a cluster of machines. <span class="hi-yl-b">Processes don't share any resources amongst themselves whereas threads of a process can share the resources allocated to that particular process, including memory address space.</span> However, languages do provide facilities to enable inter-process communication.</p>



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</div>


<div>
   # Program vs Process vs Thread   
   <div>
## Program
<p><span>A program is a set of instructions and associated data that resides on the disk and is loaded by the operating system to perform a task.</span> An executable file or a python script file are examples of programs. In order to run a program, the operating system's kernel is first asked to <span>create a new process, which is an environment in which a program is executed.</span></p>

## Process
<p><span>A process is a program in execution</span>. A process is an execution environment that consists of instructions, user-data, and system-data segments, as well as lots of other resources such as CPU, memory, address-space, disk and network I/O acquired at runtime. A program can have several copies of it running at the same time but a process necessarily belongs to only one program.</p>

## Thread
<p><span>A thread is the smallest unit of execution in a process</span> which simply executes instructions serially. A process can have multiple threads running as part of it. Usually, there would be some state associated with the process that is shared among all the threads and in turn each thread would have some state private to itself.</p> 
<p>The globally shared state amongst the threads of a process is visible and accessible to all the threads, and special attention needs to be paid when any thread tries to read or write to this global shared state. There are several constructs offered by various programming languages to guard and discipline the access to this global state, which we will go into further detail in upcoming lessons.</p>

## Notes
<p><span>Note that a "program" and a "process" are often used interchangeably, though most of the time the intent is to refer to a process.</span></p>

<p>There's also the concept of "multiprocessing" systems, where multiple processes get scheduled on more than one CPU. Usually, this requires hardware support, where a single system comes with multiple cores or the execution takes place in a cluster of machines. <span>Processes don't share any resources amongst themselves whereas threads of a process can share the resources allocated to that particular process, including memory address space.</span> However, languages do provide facilities to enable inter-process communication.</p>



</div>
</div>


This lesson discusses the differences between a program, process, and a thread. Also included is an psuedocode-example of a thread-unsafe program.

The Basics

Threading Module

Multiprocessing

Concurrent Package

Async.io

Global Interpreter Lock

Interview Practise Problems

The End

Program vs Process vs Thread

Program vs Process vs Thread

Program

Process