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‎README.md

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## [MySQLdb](content/MySQLdb.md)
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## [pymysql](content/pymysql.md)
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## [os](content/os.md)
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## [shutil](content/shutil.md)
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## [urllib2](content/urllib2.md)
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## [ ] [urllib3](content/urllib3.md)
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## [tempfile](content/tempfile.md)
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## [httplib](content/httplib.md)
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## [turtle](content/turtle.md)
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## [py-spy](content/py-spy.md)
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## [tqdm](content/tqdm.md)
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## [tools](content/tools.md)
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## [Other_thing](content/other_thing.md)

‎code/ast_eval_demo.py

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# -*- coding: utf-8 -*-
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import ast
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if __name__ == '__main__':
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# 赋值操作不能有
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# print ast.literal_eval("a=1")
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# print eval("a=1")
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# a = 1
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# 加减乘除都不能有
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# print ast.literal_eval("1+1")
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# print eval("1+1")
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# print ast.literal_eval("1==1")
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print eval("1==1")
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print ast.literal_eval("1")
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print ast.literal_eval("None")
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# 连集合都不能有
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# print ast.literal_eval("{1,2,4}")
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# print ast.literal_eval("set([1])")
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# print ast.literal_eval("[1,2,{'1', 2, '2,3,4'}, [4,5,'6']]")
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# print [1,2,{'1', 2, '2,3,4'}, [4,5,'6']]
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print ast.literal_eval("[1,2,3,{2:3}]")
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# 连最终结果是一个list也不行
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# print ast.literal_eval("list([1,2,3])")
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print list([1, 2, 3])
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# print ast.literal_eval("[1,2+3]")
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# 复数可以有，负数也可以有
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print ast.literal_eval("1+2j")
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print ast.literal_eval("-2")
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# print ast.literal_eval("--2")
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# 正数就不行
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# print ast.literal_eval("+2")
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# print ast.literal_eval("++2")

‎code/ftplib_upload.py

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#coding=utf-8
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# coding=utf-8
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import ftplib
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‎code/pymysql_demo.py

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# -*- coding: utf-8 -*-
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import pymysql
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connection = pymysql.connect(host='localhost',
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user='user',
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password='passwd',
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db='db',
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charset='utf8mb4',
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cursorclass=pymysql.cursors.DictCursor)
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with connection.cursor() as cursor:
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sql = "INSERT INTO `users` (`email`, `password`) VALUES (%s, %s)"
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# 插入单行数据
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cursor.execute(sql, ('webmaster@python.org', 'very-secret'))
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# 插入多行数据
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cursor.executemany(sql, [
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('developer@python.org', 'medium-secret'),
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('support@python.org', 'low-secret')
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])
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try:
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connection.commit()
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except Exception as e:
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print(repr(e))
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connection.rollback()
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with connection.cursor() as cursor:
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sql = "SELECT `id`, `password` FROM `users` WHERE `email`=%s"
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cursor.execute(sql, ('webmaster@python.org',))
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result = cursor.fetchone()
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print(result)
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# 使用 DictCursor 可以将 fetch 到的结果转化成 dict 格式
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print(result['id'])
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sql = "SELECT * from users;"
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cursor.execute(sql)
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result = cursor.fetchall()
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print([d['email'] for d in result])
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# 最后别忘了关闭连接
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connection.close()

‎code/tempfile_demo.py

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# -*- coding: utf-8 -*-
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import tempfile
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# create temp file
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print(tempfile.mktemp())
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# create a temporary file and write some data to it
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fp = tempfile.TemporaryFile()
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fp.write(b'Hello world!')
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# read data from file
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fp.seek(0)
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print(fp.read())
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# close the file, it will be removed
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fp.close()
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# create a temporary file using a context manager
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with tempfile.TemporaryFile() as fp:
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fp.write(b'Hello world!')
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fp.seek(0)
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print(fp.read())
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# file is now closed and removed
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# python 3
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# create a temporary directory using the context manager
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# with tempfile.TemporaryDirectory() as tmpdirname:
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# print('created temporary directory', tmpdirname)
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# directory and contents have been removed

‎code/tqdm_demo.py

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# coding=utf-8
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import time
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from tqdm import trange, tqdm
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for i in trange(10):
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time.sleep(0.1)
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for i in tqdm(range(100)):
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time.sleep(0.1)

‎code/tqdm_example.py

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# coding=utf-8
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import time
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import random
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from tqdm import tqdm
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count = 0
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total = 1024
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progress = tqdm(total=total, unit='B',unit_scale=True, desc='filename')
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while count < total:
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time.sleep(1)
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step = random.randrange(100)
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count += step
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progress.update(step)
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progress.close()

‎code/udp_and_tcp_server.py

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# -*- coding: utf-8 -*-
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import socket
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import select
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host = '127.0.0.1'
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port = 8780
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tcp_server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
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tcp_server.bind((host, port))
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tcp_server.listen(5)
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udp_server = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
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udp_server.bind((host, port))
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inputs = [tcp_server, udp_server]
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if __name__ == '__main__':
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print("Concurrent Listening on {}:{}, Press Ctrl-C to stop".format(host, port))
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while True:
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rs, ws, es = select.select(inputs, [], [])
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for r in rs:
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if r is tcp_server:
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c, addr = tcp_server.accept()
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print('[TCP] Got connection from {}:{}'.format(*addr))
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inputs.append(c)
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elif r is udp_server:
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data, addr = udp_server.recvfrom(1024)
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print('[UDP] Got message: {} from {}:{}'.format(data, *addr))
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udp_server.sendto('[UDP] {}'.format(data), addr)
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else:
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try:
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data = r.recv(1024)
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disconnected = not data
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except socket.error:
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disconnected = True
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if disconnected:
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print('[TCP] {}:{} disconnected.'.format(*r.getpeername()))
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inputs.remove(r)
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else:
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print('[TCP] Got message: {} from {}:{}'.format(data, *r.getpeername()))
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r.send('[TCP] {}'.format(data))

‎content/ast.md

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```
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有一个好消息是 3.9 开始支持 `ast.unparse` 反解析函数。
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有一个好消息是 Python 3.9 开始支持 `ast.unparse` 反解析函数。
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### 安全的执行
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在 Python 中有 `eval` 方法,但是一般如果直接调用 `eval` 执行的话，会有安全风险，可以试下 `ast.literal_eval` 进行安全的代码执行。
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这个代码执行可以厉害了`୧(๑•̀◡•́๑)૭ `， 只能含有 Python 基本数据类型，数字，字符串，列表，字典，元组，布尔值，`None` 和复数。
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> 😂，复数？是不是突然觉得很突然，为什么会有复数？你是不是已经把复数是啥给忘了？`1+2j` 就是复数。
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```python
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def literal_eval(node_or_string):
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"""
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Safely evaluate an expression node or a string containing a Python
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expression. The string or node provided may only consist of the following
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Python literal structures: strings, numbers, tuples, lists, dicts, booleans,
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and None.
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"""
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_safe_names = {'None': None, 'True': True, 'False': False}
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if isinstance(node_or_string, basestring):
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node_or_string = parse(node_or_string, mode='eval')
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if isinstance(node_or_string, Expression):
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node_or_string = node_or_string.body
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def _convert(node):
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if isinstance(node, Str):
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return node.s
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elif isinstance(node, Num):
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return node.n
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elif isinstance(node, Tuple):
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return tuple(map(_convert, node.elts))
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elif isinstance(node, List):
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return list(map(_convert, node.elts))
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elif isinstance(node, Dict):
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return dict((_convert(k), _convert(v)) for k, v
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in zip(node.keys, node.values))
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elif isinstance(node, Name):
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if node.id in _safe_names:
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return _safe_names[node.id]
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elif isinstance(node, BinOp) and \
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isinstance(node.op, (Add, Sub)) and \
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isinstance(node.right, Num) and \
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isinstance(node.right.n, complex) and \
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isinstance(node.left, Num) and \
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isinstance(node.left.n, (int, long, float)):
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left = node.left.n
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right = node.right.n
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if isinstance(node.op, Add):
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return left + right
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else:
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return left - right
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raise ValueError('malformed string')
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return _convert(node_or_string)
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```
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源码很简单，可以直接看代码，或者手动测试。
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赋值操作不能用，加减乘除不能用，比较运算不能用，连集合都不能用。复数可以用，负数也可以，但是正数就不行。
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> 好消息是从 Python 3.2 开始支持集合。
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```python
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# -*- coding: utf-8 -*-
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import ast
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if __name__ == '__main__':
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# 赋值操作不能有
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# print ast.literal_eval("a=1")
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# print eval("a=1")
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# a = 1
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# 加减乘除都不能有
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# print ast.literal_eval("1+1")
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# print eval("1+1")
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# print ast.literal_eval("1==1")
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print eval("1==1")
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print ast.literal_eval("1")
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print ast.literal_eval("None")
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# 连集合都不能有
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# print ast.literal_eval("{1,2,4}")
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# print ast.literal_eval("set([1])")
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# print ast.literal_eval("[1,2,{'1', 2, '2,3,4'}, [4,5,'6']]")
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# print [1,2,{'1', 2, '2,3,4'}, [4,5,'6']]
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print ast.literal_eval("[1,2,3,{2:3}]")
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# 连最终结果是一个list也不行
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# print ast.literal_eval("list([1,2,3])")
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print list([1, 2, 3])
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# print ast.literal_eval("[1,2+3]")
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# 复数可以有，负数也可以有
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print ast.literal_eval("1+2j")
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print ast.literal_eval("-2")
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# print ast.literal_eval("--2")
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# 正数就不行
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# print ast.literal_eval("+2")
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# print ast.literal_eval("++2")
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```
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‎content/marshmallow.md

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- exclude 排除部分字段
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- strict 参数无效时，是否报错
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- error_messages 自定义错误信息
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- many 转化为 list
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- many 可以将转化为在 nested 中传入 object list
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- `load_only` 或者 `dump_only` 都是字面意思
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- attribute 别名，这个就很神奇。在 `load` 中表示 `load_to`, 在 `dump` 中表示 `dump_from`
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- 在 python3 中 ，marshmallow 统一去除了 `load_from` 和 `dump_to` 字段，用 `data_key` 来表述
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- load_only 或者 `dump_only` 字面意思
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- 在 python3 中，marshmallow 统一去除了 `load_from` 和 `dump_to` 字段，用 `data_key` 来表述
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- 在 python3 中，missing 和 default 的作用时间发生了改变，传入`missing={}` load 的结果就是`{}` 而不是会继续 deserialize
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除了基本数据类型，如 Str, Int, Float, Dict, List 等，还有组合结构类型 Nested 和函数转化 Function 等。
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‎content/pickle.md

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pickle 与 json 的区别，json 的 dumps 和 loads 的返回都是字典，而 pickle 可以是对象，将对象 dumps 然后 loads 出来。
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pickle 返回的对象是 完全的重现传入的对象，不仅仅是构造参数，类属性和实例属性。还有私有变量和挂载的的变量方法。
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所以在缓存装饰器中，一般使用 pickle 做数据对象的序列化和反序列化，来实现数据的装载和卸载。

‎content/py-spy.md

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## py-spy
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python 性能分析工具，可以用来生成火焰图，查看程序代码性能瓶颈，或者动态查看代码运行时间消耗。
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### record
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生成火焰图，🔥
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```
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py-spy record -o profile.svg --pid 12345
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# OR
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py-spy record -o profile.svg -- python myprogram.py
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```
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### top
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查看程序运行时
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```
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py-spy top --pid 12345
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# OR
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py-spy top -- python myprogram.py
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```
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### dump
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查看函数调用堆栈
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```
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py-spy dump --pid 12345
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```
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### 火焰图
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查看火焰图中占比最大的代码行数进行分析。
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[如何读懂火焰图？](http://www.ruanyifeng.com/blog/2017/09/flame-graph.html)
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### pyflame
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pyflame 工具也可以用来生成火焰图做性能分析，就是用起来比较麻烦。

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