(Chilkat2-Python) DynamoDB - UpdateItem

Edits an existing item's attributes, or adds a new item to the table if it does not already exist. You can put, delete, or add attribute values. You can also perform a conditional update on an existing item (insert a new attribute name-value pair if it doesn't exist, or replace an existing name-value pair if it has certain expected attribute values).

For more information, see https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_UpdateItem.html

Chilkat2 Python Downloads install with pip pip3 install chilkat2 or download... Python Module for Windows, Linux, Alpine Linux, MacOS, Solaris

import sys
import chilkat2

rest = chilkat2.Rest()

# Implements the following CURL command:

# curl -X POST https://dynamodb.us-west-2.amazonaws.com/ \
#   -H "Accept-Encoding: identity" \
#   -H "Content-Type: application/x-amz-json-1.0" \
#   -H "Authorization: AWS4-HMAC-SHA256 Credential=<Credential>, SignedHeaders=<Headers>, Signature=<Signature>" \
#   -H "X-Amz-Date: <Date>" \
#   -H "X-Amz-Target: DynamoDB_20120810.UpdateItem" \
#   -d '{
#     "TableName": "Thread",
#     "Key": {
#         "ForumName": {
#             "S": "Amazon DynamoDB"
#         },
#         "Subject": {
#             "S": "Maximum number of items?"
#         }
#     },
#     "UpdateExpression": "set LastPostedBy = :val1",
#     "ConditionExpression": "LastPostedBy = :val2",
#     "ExpressionAttributeValues": {
#         ":val1": {"S": "alice@example.com"},
#         ":val2": {"S": "fred@example.com"}
#     },
#     "ReturnValues": "ALL_NEW"
# }'

# Use the following online tool to generate REST code from a CURL command
# Convert a cURL Command to REST Source Code

authAws = chilkat2.AuthAws()
authAws.AccessKey = "AWS_ACCESS_KEY"
authAws.SecretKey = "AWS_SECRET_KEY"
# Don't forget to change the region to your particular region. (Also make the same change in the call to Connect below.)
authAws.Region = "us-west-2"
authAws.ServiceName = "dynamodb"
# SetAuthAws causes Chilkat to automatically add the following headers: Authorization, X-Amz-Date
rest.SetAuthAws(authAws)

# URL: https://dynamodb.us-west-2.amazonaws.com/
bTls = True
port = 443
bAutoReconnect = True
success = rest.Connect("dynamodb.us-west-2.amazonaws.com",port,bTls,bAutoReconnect)
if (success != True):
    print("ConnectFailReason: " + str(rest.ConnectFailReason))
    print(rest.LastErrorText)
    sys.exit()

# Note: The above code does not need to be repeatedly called for each REST request.
# The rest object can be setup once, and then many requests can be sent.  Chilkat will automatically
# reconnect within a FullRequest* method as needed.  It is only the very first connection that is explicitly
# made via the Connect method.

# Use this online tool to generate code from sample JSON:
# Generate Code to Create JSON

# The following JSON is sent in the request body.

# {
#   "TableName": "Thread",
#   "Key": {
#     "ForumName": {
#       "S": "Amazon DynamoDB"
#     },
#     "Subject": {
#       "S": "Maximum number of items?"
#     }
#   },
#   "UpdateExpression": "set LastPostedBy = :val1",
#   "ConditionExpression": "LastPostedBy = :val2",
#   "ExpressionAttributeValues": {
#     ":val1": {
#       "S": "alice@example.com"
#     },
#     ":val2": {
#       "S": "fred@example.com"
#     }
#   },
#   "ReturnValues": "ALL_NEW"
# }

json = chilkat2.JsonObject()
json.UpdateString("TableName","Thread")
json.UpdateString("Key.ForumName.S","Amazon DynamoDB")
json.UpdateString("Key.Subject.S","Maximum number of items?")
json.UpdateString("UpdateExpression","set LastPostedBy = :val1")
json.UpdateString("ConditionExpression","LastPostedBy = :val2")
json.UpdateString("ExpressionAttributeValues.:val1.S","alice@example.com")
json.UpdateString("ExpressionAttributeValues.:val2.S","fred@example.com")
json.UpdateString("ReturnValues","ALL_NEW")

rest.AddHeader("Content-Type","application/x-amz-json-1.0")
rest.AddHeader("X-Amz-Target","DynamoDB_20120810.UpdateItem")
rest.AddHeader("Accept-Encoding","identity")

sbRequestBody = chilkat2.StringBuilder()
json.EmitSb(sbRequestBody)
sbResponseBody = chilkat2.StringBuilder()
success = rest.FullRequestSb("POST","/",sbRequestBody,sbResponseBody)
if (success != True):
    print(rest.LastErrorText)
    sys.exit()

respStatusCode = rest.ResponseStatusCode
print("response status code = " + str(respStatusCode))
if (respStatusCode >= 400):
    print("Response Status Code = " + str(respStatusCode))
    print("Response Header:")
    print(rest.ResponseHeader)
    print("Response Body:")
    print(sbResponseBody.GetAsString())
    sys.exit()

jsonResponse = chilkat2.JsonObject()
jsonResponse.LoadSb(sbResponseBody)

jsonResponse.EmitCompact = False
print(jsonResponse.Emit())

# Sample JSON response:
# (Sample code for parsing the JSON response is shown below)

# {
#   "Attributes": {
#     "LastPostedBy": {
#       "S": "alice@example.com"
#     },
#     "ForumName": {
#       "S": "Amazon DynamoDB"
#     },
#     "LastPostDateTime": {
#       "S": "20130320010350"
#     },
#     "Tags": {
#       "SS": [
#         "Update",
#         "Multiple Items",
#         "HelpMe"
#       ]
#     },
#     "Subject": {
#       "S": "Maximum number of items?"
#     },
#     "Views": {
#       "N": "5"
#     },
#     "Message": {
#       "S": "I want to put 10 million data items to an Amazon DynamoDB table.  Is there an upper limit?"
#     }
#   }
# }

# Sample code for parsing the JSON response...
# Use the following online tool to generate parsing code from sample JSON:
# Generate Parsing Code from JSON

AttributesLastPostedByS = jsonResponse.StringOf("Attributes.LastPostedBy.S")
AttributesForumNameS = jsonResponse.StringOf("Attributes.ForumName.S")
AttributesLastPostDateTimeS = jsonResponse.StringOf("Attributes.LastPostDateTime.S")
AttributesSubjectS = jsonResponse.StringOf("Attributes.Subject.S")
AttributesViewsN = jsonResponse.StringOf("Attributes.Views.N")
AttributesMessageS = jsonResponse.StringOf("Attributes.Message.S")
i = 0
count_i = jsonResponse.SizeOfArray("Attributes.Tags.SS")
while i < count_i :
    jsonResponse.I = i
    strVal = jsonResponse.StringOf("Attributes.Tags.SS[i]")
    i = i + 1