Summary of studying Python to use AWS Lambda

AWS Lambda Python !!!

Weekend update, Yoshida. AWS Lambda uses Python because node async is too over-technology for me (I didn't have the option of Java). I've written AWS Lambda functions so much, and I've figured out how to use them, so I've summarized the ones I use often.

import Module to use

import module name

Import in the format of. There are various external modules in Python that can be used by importing them. I think that boto3 is the most used for AWS Lambda. boto is a Python version of the SDK for working with AWS APIs.

sample

import boto3
ec2 = boto3.resource('ec2')

Module name. Method ('give argument')

You should be able to use it if you use it like this. In the above example, by storing it in the variable [ec2], the ec2 method can be used in ec2.hogehoge.

variable

Using variables in Python

variable

variable= 'hogehoge'

Use like. There is no need to declare types like Java.

Since Python doesn't have constants, it seems that variables in all uppercase letters are constants.

Array

List type variables are used as follows

Array

array = ["hoge","fuga","bar"]

Array uses [] Since the elements of the array are stored from 0, to access the element "hoge" in the above example

sample

array = ["hoge","fuga","bar"]
sample = array[0]

If you do like this, the element number 0 (hoge) of array will be stored in sample.

__Adding elements to the array __ You can add an element to the end of an array (list) by using .append

array = ["hoge","fuga","bar"]
array.append("hogeeeee")

By doing this, the array will be

array = ["hoge","fuga","bar","hogeeeee"]

It will be.

__ Remove elements from array __ You can delete the elements of the array (list) by using .pop. Deletes the specified element with .pop (element number). If .pop () and element number are not specified, the end will be deleted. .pop returns the deleted element

array = ["hoge","fuga","bar","hogeeeee"]
var = array.pop()

array = ["hoge","fuga","bar"] var = "hogeeeee"

It will be like this.

Dictionary type array

__ I want to keep a set of keys and values as an array and specify the keys to set the values __ The dictionary type is used in such cases.

dic = {"id":"i-hogehoge","type":"4xlarge"}

I use it like this. Unlike the list type, it can be used as a dictionary type by enclosing it in {}.

Fetch the value for the key

dic = {"id":"i-hogehoge","type":"4xlarge"}
dic["id"]

i-hogehoge

Get the value for the key with __dictionary array name [key name] __.

Use the __len () __ function to get the total prime number of a dictionary array.

dic = {"id":"i-hogehoge","type":"4xlarge"}
dic_num = len(dic)

Convenient when turning around with a for statement __ By the way, all dictionaries, lists and tuples are okay with len __

__ Add / Remove Elements __

add to

dic = {"id":"i-hogehoge","type":"4xlarge"}
dic["AZ"] = "a"
dic["type"] = "xlarge" 

dic = {"id":"i-hogehoge","type":"xlarge","AZ":"a"}

I will add it like this. Note that if you specify a key that does not exist, you will create a new one, If you specify a key that already exists, it will be overwritten.

Delete Delete with .pop (key name).

dic = {"id":"i-hogehoge","type":"4xlarge"}
dic.pop('type')

function

When using a function in Python, use def to define the function.

def

def sample1(content1, content2):
	print(content1)
	print(content2)

It looks like this. Define the arguments to pass to the function in () in de. You can specify more than one by separating them. Use the function as a function name (argument 1, argument 2). You can also return the result of the processing in the function. To return the result, use the return statement to return the processing result of the function to the caller.

sample

def lambda_handler(event, context):
	kansu_kekka = kansu1(hoge, hoge)
	
	print(kansu_kekka)
	
	
	
	
def kansu1(hikisu1, hikisu2):
	moji_1 = hikisu1
	moji_2 = hikisu2
	kekka = moji_1 + moji_2
	
	return kekka

hogehoge

It is an image like. __ If you want to return multiple values, you can use list tuple dictionary type. __

kekka_array = [hoge, bar, fuga]
retrun kekka_array

Something like this. Dictionaries and tuples have the same feeling

for statement

I personally use AWS Lambda, and as a usage of for, it feels like each that turns the elements of the list. About the method

array = ["hoge","fuga","bar","hogeeeee"]
count = len(array)

for i in range(0, count):
	<Processing you want to repeat>

if statement

type = 't2.micro'

if type == 'm4.4xlarge':
	print("NOOOOOOOOOOOO!!!!!")
elif type == 'm4.xlarge': 
	print("OK"）
else:
	print(type)
	

The comparison operator looks like this

Function: lambda_handler (event, context)

Let's move on from the basics of Python to AWS Lambda. This sentence is the most mysterious thing when I first touched AWS Lambda (Python2.7).

When AWS Lambda runs, AWS Lambda executes this function in the specified program. You can change the name of this function, but if you do, you'll have to rename the execution function in the AWS Lambda console. Unless you have a specific reason, you should use this name by default. The event specified in the argument stores the information passed to AWS Lambda when the AWS Lambda function is executed in JSON format.

When you run AWS Lambda in an event driven manner, some event information is stored in this event, so you can get the information you want by digging around this JSON.

You shouldn't worry about context for the time being. You can get useful information as described in Context Object (Python), I'm confused. Keep it in the corner of your head until you will need it. You can check it when you use it. Someday such a time will come.

I wrote it, but if you know this area and how to go crazy with JSON, I think that you can take the first step of AWS Lambda.

I wrote about JSON in this article before, so please refer to it.

I have a strong personal memo feeling, so if I brush up a little more, I'll write it on the engineer blog.