Run python Flask API on AWS EC2 through boto3 - python-3.x

Question

I'm new at AWS, so I'm building a code to create a instance from an Image and I want that at the same time that this EC2 is created it run a pyhton code like this:
python /folder/folder2/api_flask.py
Here's my code on boto to create my instance.
import boto3
client = boto3.session('ec2')
client.run_instances(ImageId='ami-id_number_of_img', MinCount=1, MaxCount=1, InstanceType='t2.nano')
Thnks for your help.

Answer 1

run_instances has an option called UserData which allows you to Run commands on your Linux instance at launch.
Thus to run your code, you can try to the following:
import boto3
client = boto3.client('ec2') # not boto3.session('ec2')
client.run_instances(ImageId='ami-id_number_of_img',
MinCount=1,
MaxCount=1,
InstanceType='t2.nano',
UserData='#!/bin/bash\npython /folder/folder2/api_flask.py\n')

Answer 2

Since you mention you are new to AWS, consider using CloudFormation for provisioning AWS Infrastructure. You'll still need leverage UserData as Marcin mentioned.
MyInstance:
Type: AWS::EC2::Instance
Properties:
UserData:
Fn::Base64: !Sub |
python /folder/folder2/api_flask.py
InstanceType: t2.nano
ImageId: ami-id_number_of_img
Why CloudFormation? It'd be more readable, an allows for in-place updates as well as tear downs. You could then launch the stack via boto3 (disclaimer: not tested, but demonstrates the idea):
import boto3
client = boto3.client('cloudformation')
with open('mytemplate.yml', 'r') as f:
response = client.create_stack(
StackName='my-stack',
TemplateBody=f.read())