Python--函数

[callable(obj) for obj in (abs, str, 13)]
[True, True, False]           #abs是函数，str是类，都可调用

def clip(text:str, max_len:‘int > 0‘=80) -> str:
    pass

from operator import itemgetter
metro_data = [
    (‘Tokyo‘, ‘JP‘, 36.933, (35.689722, 139.691667)),
    (‘Delhi NCR‘, ‘IN‘, 21.935, (28.613889, 77.208889)),
    (‘Mexico City‘, ‘MX‘, 20.142, (19.433333, -99.133333))
]       
for city in sorted(metro_data, key=itemgetter(1)):   #根据第2个字段排序
    print(city)

cc_name = itemgetter(1, 0)
for city in metro_data:
    print(cc_name(city))

from operator import methodcaller
s = ‘The time has come‘
upcase = methodcaller(‘upper‘)
upcase(s)   #‘THE TIME HAS COME‘
hiphenate = methodcaller(‘replace‘, ‘ ‘, ‘-‘)
hiphenate(s)   #‘The-time-has-come‘

def cmp1(n1, n2):
    return n1 - n2
a = [1, 6, 2, 9]
print(sorted(a, key=functools.cmp_to_key(cmp1)))

from functools import lru_cache

@lru_cache(maxsize=32)
def fib(n):
    print(‘calling the fib function....‘)
    if n < 2:
        return n
    return fib(n-1) + fib(n-2)
    
if __name__ == ‘__main__‘:
    print(list([fib(n) for n in range(16)]))
    [print(func) for func in dir(fib) if not func.startswith(‘_‘)]
    print(fib.cache_info())

import functools
def add(a,b):
    return a + b
add3 = functools.partial(add,3)
print add3(4)

from functools import reduce
ret=reduce(lambda x, y: x+y, [1, 2, 3, 4, 5]) # 计算的就是((((1+2)+3)+4)+5)
print(ret)  # 15 

from functools import wraps
def my_decorator(f):
     @wraps(f)
     def wrapper(*args, **kwds):
         print(‘Calling decorated function‘)
         return f(*args, **kwds)
     return wrapper