Difference in boto3 between resource client and session

Question

I am using Python 2 7 12 in Ubuntu 16 04 LTS  I m learning how to use boto3 from the following link  https   boto3 readthedocs io en latest guide quickstart html using-boto-3  My doubt is when to use resource  client  or session  and their respective functionality

User · Accepted Answer

Here s some more detailed information on what Client  Resource  and Session are all about   Client    low-level AWS service access generated from AWS service description exposes botocore client to the developer typically maps 1 1 with the AWS service API all AWS service operations are supported by clients snake-cased method names  e g  ListBuckets API    list buckets method    Here s an example of client-level access to an S3 bucket s objects  at most 1000      import boto3  client   boto3 client  s3   response   client list objects v2 Bucket  mybucket   for content in response  Contents        obj dict   client get object Bucket  mybucket   Key content  Key        print content  Key    obj dict  LastModified         you would have to use a paginator  or implement your own loop  calling list objects   repeatedly with a continuation marker if there were more than 1000   Resource    higher-level  object-oriented API generated from resource description uses identifiers and attributes has actions  operations on resources  exposes subresources and collections of AWS resources does not provide 100  API coverage of AWS services   Here s the equivalent example using resource-level access to an S3 bucket s objects  all    import boto3  s3   boto3 resource  s3   bucket   s3 Bucket  mybucket   for obj in bucket objects all        print obj key  obj last modified    Note that in this case you do not have to make a second API call to get the objects  they re available to you as a collection on the bucket  These collections of subresources are lazily-loaded   You can see that the Resource version of the code is much simpler  more compact  and has more capability  it does pagination for you   The Client version of the code would actually be more complicated than shown above if you wanted to include pagination   Session    stores configuration information  primarily credentials and selected region  allows you to create service clients and resources boto3 creates a default session for you when needed   A useful resource to learn more about these boto3 concepts is the introductory re Invent video

User · Answer

I ll try and explain it as simple as possible  So there is no guarantee of the accuracy of the actual terms    Session is where to initiate the connectivity to AWS services  E g  following is default session that uses the default credential profile e g     aws credentials  or assume your EC2 using IAM instance profile    sqs   boto3 client  sqs   s3   boto3 resource  s3     Because default session is limit to the profile or instance profile used  sometimes you need to use the custom session to override the default session configuration  e g  region name  endpoint url  etc     e g      custom resource session must use boto3 Session to do the override my west session   boto3 Session region name    us-west-2   my east session   boto3 Session region name    us-east-1   backup s3   my west session resource  s3   video s3   my east session resource  s3      you have two choices of create custom client session   backup s3c   my west session client  s3   video s3c   boto3 client  s3   region name    us-east-1     Resource   This is the high-level service class recommended to be used  This allows you to tied particular AWS resources and passes it along  so you just use this abstraction than worry which target services are pointed to  As you notice from the session part  if you have a custom session  you just pass this abstract object than worrying about all custom regions etc to pass along  Following is a complicated example E g    import boto3  my west session   boto3 Session region name    us-west-2   my east session   boto3 Session region name    us-east-1   backup s3   my west session resource  s3   video s3   my east session resource  s3   backup bucket   backup s3 Bucket  backupbucket    video bucket   video s3 Bucket  videobucket      just pass the instantiated bucket object def list bucket contents bucket      for object in bucket objects all          print object key   list bucket contents backup bucket  list bucket contents video bucket    Client is a low level class object  For each client call  you need to explicitly specify the targeting resources  the designated service target name must be pass long  You will lose the abstraction ability   For example  if you only deal with the default session  this looks similar to boto3 resource    import boto3  s3   boto3 client  s3    def list bucket contents bucket name      for object in s3 list objects v2 Bucket bucket name          print object key   list bucket contents  Mybucket      However  if you want to list objects from a bucket in different regions  you need to specify the explicit bucket parameter required for the client    import boto3  backup s3   my west session client  s3  region name    us-west-2   video s3   my east session client  s3  region name    us-east-1      you must pass boto3 Session client and the bucket name  def list bucket contents s3session  bucket name      response   s3session list objects v2 Bucket bucket name     if  Contents  in response       for obj in response  Contents            print obj  key     list bucket contents backup s3   backupbucket   list bucket contents video s3    videobucket

[python] Difference in boto3 between resource, client, and session?

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