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Python map() and lambda() Use Cases and Examples

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 In Python, map() and lambda functions are often used together for functional programming. Here are some examples to illustrate how they work. Python map and lambda top use cases 1. Using map() with lambda The map() function applies a given function to all items in an iterable (like a list) and returns a map object (which can be converted to a list). Example: Doubling Numbers numbers = [ 1 , 2 , 3 , 4 , 5 ] doubled = list ( map ( lambda x: x * 2 , numbers)) print (doubled) # Output: [2, 4, 6, 8, 10] 2. Using map() to Convert Data Types Example: Converting Strings to Integers string_numbers = [ "1" , "2" , "3" , "4" , "5" ] integers = list ( map ( lambda x: int (x), string_numbers)) print (integers) # Output: [1, 2, 3, 4, 5] 3. Using map() with Multiple Iterables You can also use map() with more than one iterable. The lambda function can take multiple arguments. Example: Adding Two Lists Element-wise list1 = [ 1 , 2 , 3 ]
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How to Configure Firewall For an Application

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A firewall is a set of rules. When a data packet moves into or out of protected network space, its contents (in particular, information about its origin, its target, and the protocol it plans to use) are tested against the firewall rules to see if it should be allowed through.


Firewall configuration


How a Firewall concept works

Let's say that the web server has to be open to incoming web traffic from anywhere on earth using either the insecure HTTP or secure HTTPS protocol.

Because your developers and admins will need to get into the backend from time to time to do their work, you’ll also want to allow SSH traffic, but only for those people who’ll need it. Requests for any other services should be automatically refused.

A Linux machine can be configured to apply firewall rules at the kernel level through a program called iptables.

Creating table rules isn't all that difficult; the syntax can be learned without too much fuss. But, in the interest of simplifying your life, many Linux distributions have added their own higher-level tools for abstracting the job.


Firewall functionality


It is also available through hardware appliances manufactured by companies like Juniper and Cisco. Those proprietary devices run on their own operating systems with unique syntax and design.

For larger enterprise deployments involving hundreds of servers spread across multiple networks, such tools will often make a lot of sense, but there's a remarkable amount that you can accomplish with any old Linux box for a tiny fraction of the cost. 


Firewall


As you might have guessed from its name, firewalld is part of the systemd family. firewalld can be installed on Debian/Ubuntu machines, but it's there by default on Red Hat and CentOS. If you're just too excited by firewalld to even consider trying anything else, here's how to install it and get it running on Ubuntu:

# apt update # apt install firewalld

To confirm that the firewall is working, try browsing your server's web root. If the site is unreachable, then firewalld is doing its job.

You’ll use the firewall-cmd tool to manage firewalld settings from the command line. Adding the --state argument returns the current firewall status:

# firewall-cmd --state running

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