停止执行使用execfile调用的脚本

Question

是否可以在不使用if/else语句的情况下中断使用execfile函数调用的Python脚本的执行？我尝试过exit()，但它不允许main.py完成。

# main.py
print "Main starting"
execfile("script.py")
print "This should print"

# script.py
print "Script starting"
a = False

if a == False:
    # Sanity checks. Script should break here
    # <insert magic command>    

# I'd prefer not to put an "else" here and have to indent the rest of the code
print "this should not print"
# lots of lines below

Answer 1

main可以将execfile封装到try/except块中:如果需要，sys.exit会引发SystemExit异常，main可以在except子句中捕获该异常，以便继续正常执行。即，在main.py中

try:
  execfile('whatever.py')
except SystemExit:
  print "sys.exit was called but I'm proceeding anyway (so there!-)."
print "so I'll print this, etc, etc"

whatever.py可以使用sys.exit(0)或其他工具来终止自己的执行。只要源代码是execfiled和执行execfile调用的源代码之间达成一致，任何其他异常都可以很好地工作--但SystemExit特别适合，因为它的含义非常明确！

Answer 2

# script.py
def main():
    print "Script starting"
    a = False

    if a == False:
        # Sanity checks. Script should break here
        # <insert magic command>    
        return;
        # I'd prefer not to put an "else" here and have to indent the rest of the code
    print "this should not print"
    # lots of lines bellow

if __name__ ==  "__main__":
    main();

我发现Python的这一方面(the __name__ == "__main__)令人恼火。

Answer 3

普通的老式异常处理有什么问题？

scriptexit.py

class ScriptExit( Exception ): pass

main.py

from scriptexit import ScriptExit
print "Main Starting"
try:
    execfile( "script.py" )
except ScriptExit:
    pass
print "This should print"

script.py

from scriptexit import ScriptExit
print "Script starting"
a = False

if a == False:
    # Sanity checks. Script should break here
    raise ScriptExit( "A Good Reason" )

# I'd prefer not to put an "else" here and have to indent the rest of the code
print "this should not print"
# lots of lines below