Question

如果在dynamodb中使用json，我将如何在python中使用/* Font-size is fluid. It will be 16px when it reaches 300px width of the viewport and 30px when it reaches 1500px of the viewport. Beyond and below those breakpoints font-size will be also fluid but we can restrict this using @media queries. For example we can restrict that after viewport has reached the width of 1500px the font size will be set as the fixed point (e.g. 2em). */ HTML { font-family: Montserrat, sans-serif; font-size: calc(16px + (30 - 16) * (100vw - 300px) / (1500 - 300) ); } /* Notes: -*- The rem unit: * In IE9 and IE10, using rem with the shorthand `font` property will make the whole declaration invalid. Also, these two browsers don’t support rem units on pseudo elements. -*- Viewport units (vw, vh, vmin, vmax): * IE11 and Edge don’t support the vmax unit. -*- Calc: * calc with px and viewport units might not work in Safari, so we can replace px units with percentages, in order to use it with viewport units. * calc with percentages is totally broken on IE (both 11 and Edge) so you can use a regular calc() function with the em unit, followed by a -webkit-calc() function with the percentage unit */ @media screen and (min-width: 1500px) { HTML { font-size: 1.875em; /*~30px*/ } }搜索session.id == "12ghbcyg"中的任何项目？

boto3

Answer 1

以下是使用contains扫描的示例。请注意，如果桌子上有数百万件物品，扫描是一项代价高昂的操作。通常，如果您不知道分区键值，则使用扫描。即使您不知道分区键值，最推荐的解决方案是使用全局二级索引（GSI）并直接查询索引而不是表。

您可能需要浏览上述选项并确定适合您的用例的方法。

以下代码旨在介绍如何使用使用包含的SCAN API。如果您知道分区键值，则可以在QUERY API上类似地使用CONTAINS。

扫描使用包含： -

from __future__ import print_function # Python 2/3 compatibility
import boto3
from botocore.exceptions import ClientError
import json
import decimal
from boto3.dynamodb.conditions import Key, Attr

# Helper class to convert a DynamoDB item to JSON.
class DecimalEncoder(json.JSONEncoder):
    def default(self, o):
        if isinstance(o, decimal.Decimal):
            if o % 1 > 0:
                return float(o)
            else:
                return int(o)
        return super(DecimalEncoder, self).default(o)

dynamodb = boto3.resource('dynamodb', region_name='us-west-2', endpoint_url="http://localhost:8000")

table = dynamodb.Table('usertable')

print("Scanning...")

sessionData = {
        "id": "12ghbcyg",
        "foo": "bar"
       }

fe = Attr('sessions').contains(sessionData)

response = table.scan(
        FilterExpression=fe        
    )

for i in response['Items']:

    print(json.dumps(i, cls=DecimalEncoder))

while 'LastEvaluatedKey' in response:
    response = table.scan(        
        FilterExpression=fe,        
        ExclusiveStartKey=response['LastEvaluatedKey']
        )

    for i in response['Items']:
        print(json.dumps(i, cls=DecimalEncoder))

如何使用boto3在dynamodb中搜索地图列表

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