无法从python脚本获取时间

Question

我正在测试两个python脚本sunset.py，它调用gettimes.py获得两次，但我没有返回任何结果。我知道gettimes.py被称为它打印的时间，但我不能从sunset.py gettimes.py打印出来

from gettimes import main 

arg1 = '' 
arg2 = '' 

main(arg1, arg2) 

print 'Hour on ', arg1 
print 'Hour off ', arg2 

sunset.py

import ephem # to get sunrise and sunset 
import datetime # import date and time modules 
import time 
import sys 

def main(arg1, arg2): 
    here = ephem.Observer() #determine position of observer 
    here.lat = 'xx.xx085057' 
    here.lon = '-x.xx781850' 
    here.elevation = 43 #meters 
    sun = ephem.Sun() #define sun as object 

    arg1 = here.next_rising(sun).datetime().strftime('%H:%M') 
    arg2 = here.next_setting(sun).datetime().strftime('%H:%M') 
    print arg1, arg2 

if __name__=='__main__': 
    sys.exit(main(sys.argv[1], sys.argv[2])) 

我在做什么错？

Answer 1

Python不会按照您认为的方式引用参数（它不像C++引用语义）。这更像是通过指针传递;你可以改变接收到的对象的属性，但是如果你完全重新分配了这个名字，你就失去了指向原始对象的指针（并且本地名称不再与调用者有任何关系）。

当您重新分配arg1和arg2在sunset.main时，会重新触发本地名称，但调用者变量未更改。这里通常的解决办法是只返回新值，垃圾无法通过时，功能并不需要它：

def main(): 
    here = ephem.Observer() #determine position of observer 
    here.lat = 'xx.xx085057' 
    here.lon = '-x.xx781850' 
    here.elevation = 43 #meters 
    sun = ephem.Sun() #define sun as object 

    arg1 = here.next_rising(sun).datetime().strftime('%H:%M') 
    arg2 = here.next_setting(sun).datetime().strftime('%H:%M') 
    return arg1, arg2 

# I have no idea why you were passing argv stuff to main here, 
# since it's not used, but this is a not too terrible way of handling it: 
if __name__ == '__main__': 
    print(*main()) 

而且在发送方：

from gettimes import main 

arg1, arg2 = main() 

print 'Hour on ', arg1 
print 'Hour off ', arg2 

Answer 2

字符串不可变。

试试：

import ephem # to get sunrise and sunset 
import datetime # import date and time modules 
import time 
import sys 

def main(): 
    here = ephem.Observer() #determine position of observer 
    here.lat = 'xx.xx085057' 
    here.lon = '-x.xx781850' 
    here.elevation = 43 #meters 
    sun = ephem.Sun() #define sun as object 

    arg1 = here.next_rising(sun).datetime().strftime('%H:%M') 
    arg2 = here.next_setting(sun).datetime().strftime('%H:%M') 

# print arg1, arg2 
    return (arg1, arg2) 

if __name__=='__main__': 
    sys.exit(main(sys.argv[1], sys.argv[2])) 

。

from gettimes import main 


arg1, arg2 = main() 

print 'Hour on ', arg1 
print 'Hour off ', arg2