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自由自在的学习 - 云计算、移动、电子商务、金融等等等

MySQL的主从配置

  • 阿亮
  • 2019/03/11 21:32
  • 0
  • 1285

主从配置常用作考虑在主服务器上做读写操作,从服务器相当于备用节点。但也有主服务只写,slave只读这种达到读写分离。如果有多个从服务器,那其实每个从服务器可以单独来读,如数据分析、远程调用等而不暴露主库。

记得面试时问我MySQL的主从是怎样的,虽然使用过MySQL,但都是单机部署经验,随口一说结果被面试官问住了,回头亲自实践了下作个记录。

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微信刷票分析

  • 阿亮
  • 2018/10/13 12:11
  • 0
  • 3207

现在但凡商家或者一些媒体、公司有什么活动都会在比赛竞选阶段设置投票环节,一方面可能是认为这样让公众参与更有公平感、另一方面可能是想让更多人知道了解活动背后的商业目的和价值,提升品牌的公众知名度等。

这不,就连所谓的程序员大赛也设置了投票环节,而且这个环节还是前置于评委专家。本文不想对此评论过多,只是在刷票分析后的吐槽一下。下面就来简单分析下这个『第二届全球程序员节解放号杯程序员大赛』是如何来刷票的。

其实后来看了微信开发者wiki后才知道现在好多都是用的静默授权认证。相关wiki可以看这里https://mp.weixin.qq.com/wiki?t=resource/res_main&id=mp1421140842

当微信打开链接http://1024.jfh.com/mvote/detail?proId=1453 时会先向微信接口发起oauth验证,获取code。链接如下
https://open.weixin.qq.com/connect/oauth2/authorize?appid=wx7e3e7526c38cebb5&redirect_uri=https%3A%2F%2Fwww.jfh.com%2Fjfm%2Fwx%2Fmenu%2Fgame%2Fv1%2FauthOpenid%3Fbackurl%3Dhttp%3A%2F%2F1024.jfh.com%2Fmvote%2Fmobile%2Fdetail%3FproId%3D1453%26from%3Dtimeline&response_type=code&scope=snsapi_base&state=MESG

其中传的appid好理解,scope=snsapi_base其实就是静默授权,即微信上不会提示获取用户基本信息,所以可以知道他调这个接口就只是想取到open id。还有回调地址redirect_uri,这个拿到code后会在解放号的服务端做各种处理,首先肯定是调用接口拿code换access_token,其实在返回值里已经拿到open id。存数据库或者session、redis等等。

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Could not fetch URL https://pypi.python.org/simple/pyecharts/

  • 阿亮
  • 2018/09/20 22:58
  • 0
  • 1680

用virtual env后 pip安装一些个库可能会报这个

Could not fetch URL https://pypi.python.org/simple/*/: There was a problem confirming the ssl certificate: [SSL: TLSV1_ALERT_PROTOCOL_VERSION] tlsv1 alert protocol version (_ssl.c:661) - skipping

原因在于pip版本过低了,我的python2.7 用env后就是8.0,可以用下面的方法更新再重试pip install

curl https://bootstrap.pypa.io/get-pip.py | python

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libMobileGestalt MobileGestalt.c:550: no access to InverseDeviceID

  • 阿亮
  • 2018/09/15 12:48
  • 10
  • 2026

XCode debug启动时报这个:

libMobileGestalt MobileGestaltSupport.m:153: xxx does not have sandbox access for frZQaeyWLUvLjeuEK43hmg and IS NOT appropriately entitled

libMobileGestalt MobileGestalt.c:550: no access to InverseDeviceID (see )

解决方法 Edit Scheme-> Run -> Arguments, 在Environment Variables里边添加

OS_ACTIVITY_MODE = Disable

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Define global function using in jinja templates

  • 阿亮
  • 2018/08/24 20:59
  • 0
  • 1257

原文是Call a python function from jinja2, 原文中点赞数量最高的并不是完美的答案,我采用的下面的方案。

Variables can easily be created:

@app.context_processor
def example():
    return dict(myexample='This is an example')

The above can be used in a Jinja2 template with Flask like so:

{{ myexample }}

(Which outputs This is an example)

As well as full fledged functions:

@app.context_processor
def utility_processor():
    def format_price(amount, currency=u'€'):
        return u'{0:.2f}{1}'.format(amount, currency)
    return dict(format_price=format_price)

The above when used like so:

{{ format_price(0.33) }}

(Which outputs the input price with the currency symbol)

Alternatively, you can use jinja filters, baked into Flask. E.g. using decorators:

@app.template_filter('reverse')
def reverse_filter(s):
    return s[::-1]

Or, without decorators, and manually registering the function:

def reverse_filter(s):
    return s[::-1]
app.jinja_env.filters['reverse'] = reverse_filter

Filters applied with the above two methods can be used like this:

{% for x in mylist | reverse %}
{% endfor %}
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Python: 使用requests下载图片

  • 阿亮
  • 2018/08/13 19:27
  • 2
  • 2926

来自最佳答案(推荐下面第一个):
You can either use the response.raw file object, or iterate over the response.

To use the response.raw file-like object will not, by default, decode compressed responses (with GZIP or deflate). You can force it to decompress for you anyway by setting the decode_content attribute to True (requests sets it to False to control decoding itself). You can then use shutil.copyfileobj() to have Python stream the data to a file object:

import requests
import shutil

r = requests.get(settings.STATICMAP_URL.format(**data), stream=True)
if r.status_code == 200:
    with open(path, 'wb') as f:
        r.raw.decode_content = True
        shutil.copyfileobj(r.raw, f)       

To iterate over the response use a loop; iterating like this ensures that data is decompressed by this stage:

r = requests.get(settings.STATICMAP_URL.format(**data), stream=True)
if r.status_code == 200:
    with open(path, 'wb') as f:
        for chunk in r:
            f.write(chunk)

This'll read the data in 128 byte chunks; if you feel another chunk size works better, use the Response.iter_content() method with a custom chunk size:

r = requests.get(settings.STATICMAP_URL.format(**data), stream=True)
if r.status_code == 200:
    with open(path, 'wb') as f:
        for chunk in r.iter_content(1024):
            f.write(chunk)

Note that you need to open the destination file in binary mode to ensure python doesn't try and translate newlines for you. We also set stream=True so that requests doesn't download the whole image into memory first.

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mkdir -p functionality in Python

  • 阿亮
  • 2018/08/13 19:05
  • 0
  • 1877

一句话:使用os.makedirs(path)

import errno    
import os


def mkdir_p(path):
    try:
        os.makedirs(path)
    except OSError as exc:  # Python >2.5
        if exc.errno == errno.EEXIST and os.path.isdir(path):
            pass
        else:
            raise

https://stackoverflow.com/questions/600268/mkdir-p-functionality-in-python

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MongoDB: Query fields if not exists

  • 阿亮
  • 2018/08/13 19:00
  • 0
  • 1517

官方文档的解释:
Existence Check

The { item : { $exists: false } } query matches documents that do not contain the item field:

db.inventory.find( { item : { $exists: false } } )

Studio3T里的Query查询条件可以是 {downloaded:{$exists: false}} 即可以查出那些没有这个downloaded字段的数据

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