这个实现的代码在这里: Pipes in Python 代码我在这里也照样给抄过来了
def pype(x, *fs):
"""
Pipe function. Takes an initial value and any number of functions/methods.
Methods as strings. Additional args are supported for functions & methods
by suppling a step as a tuple/list with function/method as the first
element and the args as the rest. The pipe input is used as the last
argument in this case. Currently no kwargs.
"""
while fs:
f = fs[0]
args = []
if isinstance(f, (list, tuple)):
args = list(f[1:])
f = f[0]
if isinstance(f, str):
if f.startswith('.'):
x = getattr(x, f[1:])(*args)
else:
x = x[f]
elif isinstance(f, int):
x = x[f]
else:
x = f(*args + [x])
fs = fs[1:]
return x
我比较感兴趣的是这一句代码：
x = f(*args + [x])， 所以我将这个代码给修改了下,
x = f(*args, x), 得到的结果完全一样。不知道为什么他会那么写。搞不懂。
如果写成 x = f(*args, [x]) ,得到的结果也很有趣。
下面就是比较:
def pype_2(x, *fs):
"""
Pipe function. Takes an initial value and any number of functions/methods.
Methods as strings. Additional args are supported for functions & methods
by suppling a step as a tuple/list with function/method as the first
element and the args as the rest. The pipe input is used as the last
argument in this case. Currently no kwargs.
"""
while fs:
f = fs[0]
args = []
if isinstance(f, (list, tuple)):
args = list(f[1:])
f = f[0]
if isinstance(f, str):
if f.startswith('.'):
x = getattr(x, f[1:])(*args)
else:
x = x[f]
elif isinstance(f, int):
x = x[f]
else:
#difference lies here
x = f(*args, x)
fs = fs[1:]
return x
def pype_3(x, *fs):
"""
Pipe function. Takes an initial value and any number of functions/methods.
Methods as strings. Additional args are supported for functions & methods
by suppling a step as a tuple/list with function/method as the first
element and the args as the rest. The pipe input is used as the last
argument in this case. Currently no kwargs.
"""
while fs:
f = fs[0]
args = []
if isinstance(f, (list, tuple)):
args = list(f[1:])
f = f[0]
if isinstance(f, str):
if f.startswith('.'):
x = getattr(x, f[1:])(*args)
else:
x = x[f]
elif isinstance(f, int):
x = x[f]
else:
#difference lies here
x = f(*args, [x])
fs = fs[1:]
return x
def add_suffix(number, s):
return '{} is {} cool!'.format(
s,
' '.join('very' for _ in range(number))
)
print(pype(
' abc: {} ',
'.strip',
('.format', 3),
(add_suffix, 2),
'.upper',
))
print(pype_2(
' abc: {} ',
'.strip',
('.format', 3),
(add_suffix, 2),
'.upper',
))
print(pype_3(
' abc: {} ',
'.strip',
('.format', 3),
(add_suffix, 2),
'.upper',
))
结果如下：非常有意思
In [6]: %run -i /usr/local/src/py/pype.py
ABC: 3 IS VERY VERY COOL!
ABC: 3 IS VERY VERY COOL!
['ABC: 3'] IS VERY VERY COOL!
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