python学习 3笔记

merge dict

def merge(defaults, override):
    r = {}
    for k, v in defaults.items():
        if k in override:
            if isinstance(v, dict):
                r[k] = merge(v, override[k])
            else:
                r[k] = override[k]
        else:
            r[k] = v
    return r

赋值判断

k = v1 if [condition] else v2

构建字典

a = ('a', 'b', 'c')
c = (1, 2 ,3)
r = {}
for k, v in zip(a, c):
    r[k] = v

使字典支持点查找

class Dict(dict):
    def __init__(self, names=(), values=(), **kw):
        super(Dict, self).__init__(**kw)
        for k, v in zip(names, values):
            self[k] = v

    def __getattr__(self, key):
         try:
            return self[key]
         except KeyError:
            raise AttributeError(r"'Dict' object has no attribute '%s'" % key)

    def __setattr__(self, key, value):
        self[key] = value

def toDict(d):
    D = Dict()
    for k, v in d.items():
        D[k] = toDict(v) if isinstance(v, dict) else v
    return D

判断是否为函数

callable(fn)

获取其他模块变量/函数

mod = __import__(module_name, globals(), locals())
for attr in dir(mod):
    fn = getattr(mod, attr)
    if callable(fn):
        ......

参数类型判断

params = inspect.signature(fn).parameters
for name, param in params.items():
    if param.kind == inspect.Parameter.KEYWORD_ONLY:
    .....

POSITIONAL_ONLY        位置参数
POSITIONAL_OR_KEYWORD  位置参数或关键字参数
KEYWORD_ONLY           关键字参数
VAR_POSITIONAL         可变位置参数 *args
VAR_KEYWORD            可变关键字参数 **kw      

创建进程

import multiprocessing, os, time

def whoami(name):
	print("I'm %s, in process %s" % (name, os.getpid()))

def loopy(name):
	whoami(name)
	start = 1
	stop = 1000000
	for num in range(start, stop):
		print("	Number %s of %s. Honk!" % (num, stop))
		time.sleep(1)

if __name__ == '__main__':
	whoami('main')
	#创建进程
	p = multiprocessing.Process(target=loopy, args=('loopy', ))
	p.start()
	time.sleep(5)
	#终止对应进程
	p.terminate()

打开文件

file = open('demo.py', 'r', encoding='UTF-8')
try:
    for line in file:
        print(line, end='')
except:
    print('讀取檔案發生錯誤')
finally:
    file.close()

//简化
with open('demo.py', 'r', encoding='UTF-8') as file:
    for line in file:
        print(line, end='')