Creating a 'SS' item in DynamoDB using boto3 - python-3.x

Question

I'm trying to create an item in AWS DynamoDB using boto3 and regardless what I try I can't manage to get an item of type 'SS' created. Here's my code:
client = boto3.resource('dynamodb', region_name=region)
table = client.Table(config[region]['table'])
sched = {
"begintime": begintime,
"description": description,
"endtime": endtime,
"name": name,
"type": "period",
"weekdays": [weekdays]
}
table.put_item(Item=sched)
The other columns work fine but regardless what I try, weekdays always ends up as a 'S' type. For reference, this is what one of the other items look like from the same table:
{'begintime': '09:00', 'endtime': '18:00', 'description': 'Office hours', 'weekdays': {'mon-fri'}, 'name': 'office-hours', 'type': 'period'}
Trying to convert this to a Python structure obviously fails so I'm not sure how it's possible to insert a new item.

Answer 1

To indicate an attribute of type SS (String Set) using the boto3 DynamoDB resource-level methods, you need to supply a set rather than a simple list. For example:
import boto3
res = boto3.resource('dynamodb', region_name=region)
table = res.Table(config[region]['table'])
sched = {
"begintime": '09:00',
"description": 'Hello there',
"endtime": '14:00',
"name": 'james',
"type": "period",
"weekdays": set(['mon', 'wed', 'fri'])
}
table.put_item(Item=sched)

Answer 2

As follow up on #jarmod's answer:
If you want to call update_item with a String Set, then you'll insert a set via ExpressionAttributeValues property like shown below:
entry = table.put_item(
ExpressionAttributeNames={
"#begintime": "begintime",
"#description": "description",
"#endtime": "endtime",
"#name": "name",
"#type": "type",
"#weekdays": "weekdays"
},
ExpressionAttributeValues={
":begintime": '09:00',
":description": 'Hello there',
":endtime": '14:00',
":name": 'james',
":type": "period",
":weekdays": set(['mon', 'wed', 'fri'])
},
UpdateExpression="""
SET #begintime= :begintime,
#description = :description,
#endtime = :endtime,
#name = :name,
#type = :type,
#weekdays = :weekdays
"""
)
(Hint: Usage of AttributeUpdates (related Items equivalent for put_item calls) is deprecated, therefore I recommend using ExpressionAttributeNames, ExpressionAttributeValues and UpdateExpression).