python 重定向输入输出流 脚本

"""
file-like objects that save standard output text in a string and provide
standard input text from a string; redirect runs a passed-in function
with its output and input streams reset to these file-like class objects;
"""

import sys # get built-in modules

class Output: # simulated output file
def init(self):
self.text = '' # empty string when created
def write(self, string): # add a string of bytes
self.text += string
def writelines(self, lines): # add each line in a list
for line in lines: self.write(line)

class Input: # simulated input file
def init(self, input=''): # default argument
self.text = input # save string when created
def read(self, size=None): # optional argument
if size == None: # read N bytes, or all
res, self.text = self.text, ''
else:
res, self.text = self.text[:size], self.text[size:]
return res
def readline(self):
eoln = self.text.find('\n') # find offset of next eoln
if eoln == -1: # slice off through eoln
res, self.text = self.text, ''
else:
res, self.text = self.text[:eoln+1], self.text[eoln+1:]
return res

def redirect(function, pargs, kargs, input): # redirect stdin/out
savestreams = sys.stdin, sys.stdout # run a function object
sys.stdin = Input(input) # return stdout text
sys.stdout = Output()
try:
result = function(*pargs, **kargs) # run function with args
output = sys.stdout.text
finally:
sys.stdin, sys.stdout = savestreams # restore if exc or not
return (result, output) # return result if no exc