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AWS Lambda – Function in Python

In this chapter, we will create a simple AWS Lambda function in Python and understand its working concepts following detail.

Before proceeding to work on creating a Lambda function in AWS, we need AWS toolkit support for Python. For this purpose, follow the steps given below and observe the corresponding screenshots attached −

Step 1

Login to AWS console and create Lambda function and select the language as Python.

Step 2 Step 3

Now, save the changes and the test the code to see the output. You should see the following output and logs when you test it in AWS console using the test button from the UI.

Step 4

Now, you can write code inside any editor or an IDE for Python. Here, we are using visual studio code for writing the code. You should later zip the file and upload in AWS console.

Here, we have zipped the code and using it AWS console.

Step 5

Now, select Upload a .ZIP file option as shown below −

Handler Details for Python

Note that the handler has to be name of the file followed by name of the function. In the above case, our file name is chúng tôi and name of the function is my_handler; so the handler will be hellopython.my_handler.

Once the upload is done and changes are saved, it actually shows the details of the zip file in the online editor in AWS Lambda console. Now, let us test the code to see the output and logs.

Now, let us understand the details of the Lambda function using the following sample code −

def my_handler(event, context): return "aws lambda in python using zip file"

In the above code, the function name my_handler is having 2 params, event and context.

Context Object in Python

Context object gives details like the name of the Lambda function, time remaining in milliseconds, request id, cloud watch group name, timeout details etc.

The methods and attributes available on context object are shown in the tables given below −

Sr.No Method Name & Description

1

get_remaining_time_in_millis()

This method gives the remaining time in milliseconds until the lambda function terminates the function

Sr.No Attribute & Description

1

function_name

This gives aws lambda function name

2

function_version

This gives the version of aws lambda function executing

3

invoked_function_arn

This will gives ARN details.

4

memory_limit_in_mb

This shows the memory limit added while creating lambda function

5

aws_request_id

This gives the aws request id.

6

og_group_name

This will give the name of the cloudwatch group name

7

log_stream_name

This will give the name of the cloudwatch log stream name where the logs are written.

8

identity

This will give details about amazon cognito identity provider when used with aws mobile sdk. Details given are as follows −

identity.cognito_identity_id

identity.cognito_identity_pool_id

9

client_context

This will details of the client application when used with aws mobile sdk. The details given are as follows −

client_context.client.installation_id

client_context.client.app_title

client_context.client.app_version_name

client_context.client.app_version_code

client_context.client.app_package_name

client_context.custom – it has dict of custom values from the mobile client app

client_context.env – it has dict of environment details from the AWS Mobile SDK

Let us see a working example in Python which outputs the context details. Observe the code given below −

def my_handler(event, context): print("Log stream name:", context.log_stream_name) print("Log group name:", context.log_group_name) print("Request ID:",context.aws_request_id) print("Mem. limits(MB):", context.memory_limit_in_mb) print("Time remaining (MS):", context.get_remaining_time_in_millis()) return "aws lambda in python using zip file"

The corresponding output of the code shown above is given below −

Logging using Python

To log info using Python, we can use print or logger function available. Let us use the above example of context and check inCloudWatch to see if the logs are printed. Observe the following code −

def my_handler(event, context): print("Log stream name:", context.log_stream_name) print("Log group name:", context.log_group_name) print("Request ID:",context.aws_request_id) print("Mem. limits(MB):", context.memory_limit_in_mb) print("Time remaining (MS):", context.get_remaining_time_in_millis()) return "aws lambda in python using zip file"

The output of this code in CloudWatch is as shown below −

Observe the following example to understand about using logger to print logs to CloudWatch −

import logging logger = logging.getLogger() logger.setLevel(logging.INFO) def my_handler(event, context): logger.info('Using logger to print messages to cloudwatch logs') return "aws lambda in python using zip file"

The output for this will be as shown in the screenshot given below −

Error Handling in Python for Lambda function

In this section, let us see a working example which shows how to handler errors in Python. Observe the piece of code given here −

def error_handler(event, context): raise Exception('Error Occured!')

The log display is as shown in the image here −

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Using The Main() Function In Python

The main function is not required for every Python program, but it is recommended to use it for better organization and readability of the code. It is especially useful for larger programs where there are multiple functions and classes.

How to Use the Main Function

To use the main function in Python, you need to define it in your program. The main function can have any name, but it is conventionally named main. The main function can also take arguments, but it is not required.

Here is an example of a simple Python program that uses the main function:

def main(): print("Hello, World!") if __name__ == "__main__": main()

In this program, we define the main function that prints the string “Hello, World!” to the console. We then use the if __name__ == "__main__": statement to check if the program is being run as the main program. If it is, we call the main function.

The if __name__ == "__main__": statement is used to check if the module is being run as the main program. This is required because sometimes you may want to import a module into another program, and you don’t want the code in the main function to be executed.

Here are a few more examples of how to use the main function in Python:

Example 1: Taking Command-Line Arguments import sys def main(): name = sys.argv[1] print(f"Hello, {name}!") else: print("Hello, World!") if __name__ == "__main__": main()

In this program, we import the sys module to access the command-line arguments. We then check if there are any arguments passed to the program using len(sys.argv). If there is at least one argument, we print a personalized string. Otherwise, we print “Hello, World!”.

To run this program with a command-line argument, you can run the following command:

python chúng tôi John

This will print “Hello, John!” to the console.

Example 2: Using Classes class Person: def __init__(self, name): chúng tôi = name def say_hello(self): print(f"Hello, {self.name}!") def main(): person = Person("John") person.say_hello() if __name__ == "__main__": main()

In this program, we define a Person class that has a name attribute and a say_hello method. We then create a Person object with the name “John” and call the say_hello method.

Example 3: Using Modules import my_module def main(): my_module.say_hello() if __name__ == "__main__": main()

In this program, we import a module named my_module that contains a say_hello function. We then call the say_hello function from the main function.

Example 4: Using Libraries import requests def main(): print(response.status_code) if __name__ == "__main__": main()

In this program, we import the requests library to make a GET request to Google’s homepage. We then print the status code of the response.

Example 5: Using Context Managers with open("file.txt", "w") as f: f.write("Hello, World!") def main(): with open("file.txt", "r") as f: print(f.read()) if __name__ == "__main__": main()

In this program, we use a context manager to open a file named “file.txt” in write mode and write “Hello, World!” to it. We then use another context manager to open the same file in read mode and print its contents.

Conclusion

How Python Eval Function Work With Examples

Introduction to Python eval()

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Syntax:

eval(expression, globals=None, locals=None)

Explanation:

Eval() function usually needs 3 parameters, but the 2nd and 3rd parameter terms are optional/not much important than the 1st parameter. The 3 parameters are expression, globals, and locals.

Expression parameter: This is the string that is as parsed and also evaluated as the Python expression.

Globals parameter ( dictionary parameter ): This parameter is a dictionary, and this parameter is also optional. Nothing happens even if we don’t specify this parameter in the eval() function.

Locals parameter ( Mapping Object ): This locals parameter is an object which is mapping… The dict or dictionary of the globals parameter is the best and standard mapping type in the Python Programming Language commonly.

How Python Eval Function Work with Examples

Eval() function/method will returns the value/result after evaluating the expression. eval function works by parsing the string value, and that string value also be evaluated as the python expression.

Example #1

At each and every IF statements, if the IF condition is False, then the interpreter of python goes to the ELSE condition’s statements, and the programming inside of it will be printed/interpreted etc.. all at a time, but the program inside of the ELSE condition is also be interpreted every line one by one.

Code:

x = 10 print(eval('x')) print(eval('x+10')) print(eval('x*x')) print(eval('x*x*x')) if(x%2==0): print('X is even number') if(x%2!=0): if(x%3!=0): if(x%5!=0): if(x%7!=0): print(eval('x')) print('is a prime number') else: print ('x is not prime number') else: print('x is not prime number') else: print('x is not prime number') else: print('x is not prime number')

Output:

Example #2

Now we enter the try, except concept. These are just like the IF and ELSE condition. If the “try” has correct parameters, then try to run properly and exits from the program, or else the except concept comes into the picture. Try, except concept will be very helpful to handle errors and usage of the eval() function/functions. Statements that are in the try will print the eval() function, which has math functions “square root” and the power of x and y values which are about to declare manually by the user. If the input doesn’t contain any input as needed with the mentioned math functions, the result will be printed, and the loop once again runs and asks again for the input, or else you can just enter and go the except concept. There you will print the ext1 value, and the interpreter breaks out and comes out from the except concept. Then the print statement will print “Now it is Done” like that.

Code:

from math import * for lm in range(1, 3): func1 = input("Enter the Math Function which are mentioned below to Evaluate.nFunctions Allowed are: 1. square_root(x) and 2. power(x,y):n") try: print(eval(func1, {'square_root': sqrt, 'power': pow})) except Exception as ex1: print(ex1) break print('Now it is Done')

Output:

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This is a guide to Python eval(). Here we discuss the introduction and working of the python eval() function along with different examples and its code implementation. You may also look at the following articles to learn more –

How List Function Works In Php

Introduction to PHP list

PHP list function is an important function used for assigning values to a list of variables while performing single operation at one go. This function is not present in all the PHP versions and is introduced exclusively in PHP versions before 7.1 which works only for numerical arrays while assigning values to the list of variables. The values assigned to the variables is the return type once executed with the help of PHP list function. PHP list function is not actually a function like array rather it is considered a language construct for assigning values.

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Syntax

list(var_1, var_2, ...)

The syntax flow is in a way where there is a list as function comprising of arguments passed from the function:

list: The function list() is declared.

var_1: The variable passed as an argument is required and is quite of mandatory in the sense this acts as the first variable to assign a value to the variable declared.

var_2: The second variable is optional and then this variable is used to assign values to the list followed by sequence.

This syntax when applied has a return type as assigned array which means whatever values are assigned to the array is the return type for that instance.

How list Function works in PHP?

list() function is an inbuild function in PHP which is exclusively used for assigning values to more than one variable by performing a single operation at the time of execution.

Let’s see the actual flow for working of list function in PHP which is described as follows :

Initially list being an inbuild function doesn’t required to be written and doesn’t require any external function call it works just seamlessly without much intrusion.

The array gets assigned with the required values from the multiple values considered at the time of execution.

There is a misconception regarding the array declared as a variable for assigning values but it’s just a myth in actual it is just a language construct.

Everything gets executed in a single operation using list() function while assigning variable.

This function works seamlessly on the numerical arrays only, which represents the fact that the user will get interacted with the arrays using first variable which is var_1.

The second argument getting passed to the function is an optional argument which gets retrieved and worked once the first argument satisfies the condition.

One point needs to be kept in mind which is like the number of variables should not exceed length of the numerical array and in case it exceeds the array defined variable then it will give error with parameters types and there will be no return type at the time of execution.

There should be no exception introduced while executing this list function otherwise the requirement and the return type will not get suffice.

If a function is not having any return statement, then implicitly it will return NULL as its return type at the time of execution.

The parameters to be passed as part of the function should be arranged in a way where the list of variables will get separated by spaces within the code.

The first variable to be passed from the function is a mandatory variable for the return type.

Another important point to look upon is the version compatibility which means that the PHP version should have version support less than 7.

Also, coming to the version compatibility for PHP then PHP version 5 in the list should assign values starting with right most parameter.

Whereas there is a difference with PHP version 7 where the assignment to the values of variable which will appear as left-most parameter.

In case normal variables are used then there is no need to worry about assigning values to the variables and then using these arrays with indices is used for arranging the values in an order.

But in case of order must be maintained like from left to right or from right to left then it is very much need to keep in mind about the PHP versioning.

Examples of PHP list

Given below are the examples of PHP list:

Example #1

This program demonstrates the PHP list where the array is assigned with the variable having values as shown in the output.

Code:

<?php $an_arr = array(“Banana”,”Mango”,”Apple”); list($a_1, $b_2, $c_3) = $an_arr; echo “I have many fruits, one $a_1, one $b_2 and one $c_3.”;

Output:

Example #2

This program demonstrates the PHP list where array is assigned with the first and third value within the variable as shown in the output.

Code:

<?php $arr_b = array(“Pencil”,”Copy”,”Pen”); list($k_0, , $z_1) = $arr_b; echo “Used_variable_for_modification $k_0 and $z_1 variables.”;

Output:

Example #3

This program demonstrates the declaration of array in a way where initially all the variables are listed, followed by retrieving some values and then listing some of them among all from which the third one gets skipped in case of the list with all the string it will return the NULL value as shown in the output.

Code:

<?php $in_p = array(‘choco’, ‘caramel’, ‘pancake’); list($choco, $cake, $caramel) = $in_p; echo “$choco cake $color and $caramel appears relishing n”; list( , , $caramel) = $in_p; echo “caramel cake tastes wow $caramel!n”; list($choco, , $cake) = $in_p; echo “$choco has $cake.n”; list($gi_t) = “lost_in n”; list($choco, , $cake) = $in_p; echo “$choco has $cake.n”; var_dump($gi_t);

Example #4

This program demonstrates the nested array by using list function as shown in the output.

Code:

<?php list($a_1, list($b_2, $c_0)) = array(1, array(4, 6)); var_dump($a_1, $b_2, $c_0); echo “listing of nested array”;

Output:

Conclusion

PHP list is an inbuild function which gives user the flexibility and versatility to adapt this function as part of the implementation as per requirement. Use of PHP list make the values arranged in some order which gives user visibility to implement a user-friendly array return values with variables.

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This is a guide to PHP list. Here we discuss the introduction, how list function works in PHP? along with examples respectively. You may also have a look at the following articles to learn more –

How Recover() Function Works In Go Language?

Introduction to Golang recover()

Web development, programming languages, Software testing & others

Syntax:

In the below syntax we are showing a simple syntax for the recovery function of the go language, we see the below syntax attribute with the following steps.

Here error is the dynamic variable you can create with any other name according to your wish.

Recovery is a function which will handle the case of error.

We can use the panic function to display the error in the customized format.

if error := recover(); error != nil How recover() Function works in Go Language?

Before seeing the work of the recovery in go language we need to know why we need recovery, if you have seen any other programming language like java and dot net they have try and catch statement which deal with situation which is not in our hand, for example in case if we are performing division and by some way division become like number / 0 which means the output will be infinite and our system can go into blocking stage as they will not be able to handle infinite so for such type of situations we use the recovery.

Working of the recovery in the following steps:

Recovery is a function which is used inside the deferred type of function, it is not meant for use in the case of any normal function.

In case if we want to handle an error case and we are using recovery and it is not inside the deferred then it will not be able to sequences of panicking.

We have to write a function inside the import of the go language and inside this function we need to write the capturing of the exception logic.

Remember the recovery function in the go language is the inbuilt function.

Examples of Golang recover()

Given below are some of the examples which display the working of the recovery function, to execute these examples we can create a file with name chúng tôi and we can execute the file after copy pasting of the below examples. We can use the command go run chúng tôi and we will get the output.

Example #1

Below is an example where we are dealing with the panic condition without using defer, and you can see the output which totally looks like an error.

package main import "fmt" func exceptionCase() { if e := recover(); e != nil { fmt.Println("Handling the exception and exception is ", e) } } func start(school *string, school_name *string) { exceptionCase() if school == nil { panic("Error: The value of school can not be nil") } if school_name == nil { panic("Error: The school name can not be nil") } fmt.Printf("The school type is: %s n The school name is: %sn", *school_name, *school_name) fmt.Printf("Here we are returning response of success from the start function") } func main() { school_type := "Private School" start(&school_type, nil) fmt.Printf("Here we are returning the response from the main function") }

Output:

Example #2

Here we are using the recovery function along with defer and you can see the screen output, it is more understandable in nature.

Code:

package main import "fmt" func exceptionCase() { if e := recover(); e != nil { fmt.Println("Handling the exception and exception is ", e) } } func start(student_type *string, student_name *string) { defer exceptionCase() if student_type == nil { panic("Error: The value of school can not be nil") } if student_name == nil { panic("Error: The school name can not be nil") } fmt.Printf("The Student Type: %s n The student name: %sn", *student_type, *student_name) fmt.Printf("Here we are returning response of success from the start function") } func main() { student_type := "Regular Student" start(&student_type, nil) fmt.Printf("Here we are returning the response from the main function") }

Output:

Example #3

In the below example we have taken some calls test1 and test2 and used the deferred, here we are using the function recovery inside the recovery and it will be used to handle panic cases.

Code:

package main import ( "fmt" "time" ) func exceptionCase() { if e := recover(); e != nil { fmt.Println("Exception case is", e) } } func test1() { defer exceptionCase() fmt.Println("Let us greet the function test1") go test2() time.Sleep(11 * time.Second) } func test2() { fmt.Println("Let us greet the function test2") panic("Do not worry!!") } func main() { test1() fmt.Println("Here we are returning final response of main") }

Output

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This is a guide to Golang recover(). Here we discuss the introduction, syntax, and working of the recover() function in the go language along with examples and code implementation. You may also have a look at the following articles to learn more –

How Does Unpack Function Work In Perl?

Introduction to Perl unpack

Web development, programming languages, Software testing & others

Syntax:

The unpack is one of the functions that can be converted or transform the binary data type values into the user-defined data type templates with the help of representations that are related to the perl script functions, keywords, and other built-in syntax. The below codes are the basic syntax for creating and using the unpack function in the perl scripts.

#!/usr/bin/perl -w $vars= pack(""); @vars1=unpack("$vars");

—some Perl script logic codes depend upon the requirement—

How does unpack function work in Perl?

Generally, the perl script does not have to access the memory randomly. It has some structure and represents the same with some translators like a pack and unpack() functions. It has some default representations. It can be called a template like that if we use unpack() function; it seems like the opposite process of the pack() function. The binary data with some specific structures has its own reference of each value stored in the memory. So the pack function contains the specific format for listing out the values and packed or converted into the character strings but unpacks takes only the format with the character strings with some breaks to the strings with the specified formats and assigned with the variables in the script.

Examples

Let us discuss examples of Perl unpack.

Example #1

Code:

#!/usr/bin/perl -w $vars = pack("siva", 7849367); print "Welcome To My Domain $varsn"; $vars = pack( "" ); print "Have a Nice Day $varsn"; $vars = pack( "siva", 6354, "I", 6858 ); print "Welcome User please find your packed values $varsn"; @vars1 = unpack( "siva", "$vars" ); print "Thank You User your first Input user values $vars1[0]n"; print "Thank You User your second Input user values $vars1[1]n"; print "Thank You User your third Input user values $vars1[2]n"; print "Thank You User your first Input user values $vars1[3]n";

Output:

In the above example, we used the pack() and unpack() function at the time, and also we can use the variable like $vars. We assigned the value to the specific variable and used the pack and unpack() function based on their needs.

Example #2

Code:

#! perl -w use strict; sub exa { shift; } sub demo1 { unpack "i*", shift; } sub demo2 { unpack "V*", shift; } sub demo3 { unpack "I*", shift; } sub demo4 { unpack "a*", shift; } sub demo5 { unpack "b*", shift; } sub demo6 { unpack "c*", shift; } sub demo7 { unpack "d*", shift; } sub demo8 { unpack "h*", shift; } sub demo9 { unpack "l*", shift; } sub demo10 { unpack "n*", shift; } sub finsa{ my $vars= shift; my $vars1 = "Welcome To My DOmain wdejfh bwefvhd gdv gv jgfjw egf wkejg jerfg jewrgf ekjwrhw kjejhrw kjergkw j ehgw ejhrgke jrgf kjergk ejhrgfkw ejhrge jhrgfkweh jrk ehjkw jerhke jh ekhrj hg"; my $vars2 = "983465 ifsdg8 shdfgh he sdjsb khbwdsh 9876asnbd 87 hjg 90 jh999 jhjhj g89 7987987 hjh j j979 8jkhj 9jh egdf gh8888 wgefh w8 hh98878 878 87 7 79 7 778 78 89 9 98 98 98 98 98 9 9 "; if ($vars3 =~ /^$vars2/i) { print "Welcome Usersn"; } else { } } finsa &exa; finsa &demo1; finsa &demo2; finsa &demo3; finsa &demo4; finsa &demo5; finsa &demo6; finsa &demo7; finsa &demo8; finsa &demo9; finsa &demo10;

Output:

Example #3

Code:

#!/usr/bin/perl -w $vars = pack("B*", 192, 168,42, 76); print "Welcome To My Domain $varsn"; @vars1 = unpack("B*", "welcomen"); print "Array $vars1[0]n";

Output:

In the final example, we used the basic pack() and unpack() functions in the ip numbers. Basically, with the help of ‘.” Operator or symbol, we can split the numbers and set it as the system’s ip address.

Conclusion

Finally, we used Perl as default control basic structures, functions, user input, and output operations. These are the concepts that are held through the script for creating the task depending upon the user’s requirement.

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This is a guide to Perl unpack. Here we discuss the introduction and How does unpack function work in Perl? with Examples for better understanding. You may also have a look at the following articles to learn more –

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