字典扁平化
目标 {'a':{'b';1,'c':2},d:{'e':3,f:{g:4}
期望 {'a.b':1,'a.c':2,'d.e':4,'d.f.g':4}
dic = {'a':{'b':1,'c':2},'d':{'e':3,'f':{'g':4}}}
dic1 = {}
def fn(dic:dict,dic1key=''):
for k,v in dic.items():
if isinstance(v,dict):
fn(v,dic1key=dic1key+ k +'.')
else:
dic1[dic1key + k] = v
fn(dic)
print(dic1)
base64编码
alphabet = b'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
def base64encode(src:str):
target = bytearray()
if isinstance(src,str):
ret = src.encode()
else:
return
length = len(ret)
r = 0 # 余下几个
for offset in range(0,length,3):
tripe = ret[offset:offset+3]
if offset + 3 > length:
r = 3 - len(tripe)
tripe = tripe + b'\x00'*r
val = int.from_bytes(tripe,'big')
for i in range(18,-1,-6):
if i == 18:
index = val >> i
else:
index = val >> i & 0x3F
target.append(alphabet[index])
for i in range(1,r+1):
target[-i] = 61
return bytes(target)
base64encode('a')
求最大公共字串
矩阵算法
str1 = 'abcdef'
str2 = 'defabcd'
def fn(str1:str,str2:str):
if len(str1) > len(str2):
str1,str2 = str2 ,str1
length1 = len(str1) # 最短
length2 = len(str2)
matrix = [[0]*length1 for i in range(length2)]
# print(matrix)
xmax = 0
xindex = 0
for i,x in enumerate(str2):
for j,y in enumerate(str1):
if x != y:
pass
else:
if i==0 or j==0:
matrix[i][j] = 1
else:
pre = matrix[i-1][j-1]
if pre > 0:
matrix[i][j] = pre + 1
if matrix[i][j] > xmax :
xmax = matrix[i][j]
xindex = j
# print(matrix)
# print(xmax, xindex)
start= xindex + 1 -xmax
end = xindex +1
return str1[start:end]
print(fn(str1,str2))
装饰器的应用
实现一个cache装饰器，实现可过期被清除的可能
简化设计，函数的参数定义不包含可变位置参数，可变关键字参数和keyword-only参数
可以不考虑缓存满了之后的换出问题
from functools import wraps
import inspect
import time
import datetime
def mag_cache(fn):
local_cache = {} #对不同函数名是不同的cache
@wraps(fn)
def wrapper(*args,**kwargs): #接收各种参数
expire_keys = []
for k,(_,stamp) in local_cache.items():
if (datetime.datetime.now().timestamp() - stamp) > 5:
expire_keys.append(k)
for k in expire_keys:
local_cache.pop(k)
# 参数处理，构建key
sig = inspect.signature(fn)
params = sig.parameters # 有序字典
params_dict = {}
values = list(params.values()) # 有序的
keys = list(params.keys())
#位置传参
# for i,x in enumerate(args):
# params_dict[keys[i]] = v
params_dict.update(zip(params.keys(),args))
# 关键字传参
params_dict.update(kwargs)
# 缺省值
for k,v in params.items():# 定义的所有参数
if k not in params_dict:
params_dict[k] = v.default
key = tuple(sorted(params_dict.items())) # 判断是否需要缓存
print(key)
if key not in local_cache.keys():
local_cache[key] = fn(*args,**kwargs),datetime.datetime.now().timestamp()
return local_cache[key]
return wrapper
@mag_cache
def add(x=4,y=5):
time.sleep(3)
return x+y
命令分发器
程序员可以方便的注册函数到某一个命令，用户输入命令时，路由到注册的函数
如果此命令没有对应的注册函数，执行默认函数
用户输入用input(">>")
def cmd_dispatcher(): #封装
cmd_dict = {}
def reg(cmd):
def _reg(fn):
cmd_dict[cmd] = fn
return fn
return _reg
@reg('default_func')
def default_func():
print('default')
return
def dispatcher():
while True:
cmd = input('>>')
if cmd == 'quit':
return
cmd_dict.get(cmd, default_func)()
return reg, dispatcher #封装
reg, dispatcher = cmd_dispatcher() #封装&解构
@reg('add')
def add(): #add=reg('add')(add)
print(1)
return
dispatcher()
