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# coding: utf-8

import sys
import re

def lex(characters, token_exprs):
    pos = 0
    tokens = []
    while pos < len(characters):
        match = None

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#运行用户
user nobody;
#启动进程,通常设置成和cpu的数量相等
worker_processes  1;

#全局错误日志及PID文件
#error_log  logs/error.log;
#error_log  logs/error.log  notice;
#error_log  logs/error.log  info;

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# coding: utf-8


u"""
1.4 字符串对齐
字符串方法 ljust rjust center 参数: int 对齐符号数目 str 可以选的对齐占位符,默认为空格
"""

# 1.9 简化string translate方法使用流程
import string

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import logging, logging.config
import sys

LOGGING = {
    'version': 1,
    'handlers': {
        'console': {
            'class': 'logging.StreamHandler',
            'stream': sys.stdout,
        }

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# coding: utf-8


u"""
线性数据结构, 栈, 队列, deques, 容器结构, 数据项之间存在相对的位置
"""

class Stack(object):
    u"""
    栈 先进后出

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class ClassPropertyDescriptor(property):
    u"""
    class property descriptor
    """

    def __get__(self, obj, objtype=None):
        if self.fget is None:
            raise AttributeError("unreadable attribute")
        return self.fget.__get__(obj, objtype)()

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 # 关联字段用select_related不能用正常使用only选取关联对象的某些字段，可以变通一下
a = Articles.objects.only('title').annotate(blog_name=F('blog__name')).first()
a.title
a.blog_name

# Django group by

from django.db.models import Count
Members.objects.values('designation').annotate(dcount=Count('designation'))

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class DynamicFieldsModelSerializer(serializers.ModelSerializer):
    """
    A ModelSerializer that takes an additional `fields` argument that
    controls which fields should be displayed.
    """

    def __init__(self, *args, **kwargs):
        # Don't pass the 'fields' arg up to the superclass
        fields = kwargs.pop('fields', None)

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from django.contrib.auth.models import Permission, User

def get_user_permissions(user):
    if user.is_superuser:
        return Permission.objects.all()
    return Permission.objects.filter(Q(group__user=user)|Q(user=user)).distinct()

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from django.db.models import Aggregate
from django.db.models.sql import aggregates


def custom_aggregation(select_query):
    class SqlAggregate(aggregates.Aggregate):
        sql_function = ''
        sql_template = select_query

    class VisitorRate(Aggregate):