Multiple try codes in one block

问题

I have a problem with my code in the try block. To make it easy this is my code:

try:
    code a
    code b #if b fails, it should ignore, and go to c.
    code c #if c fails, go to d
    code d
except:
    pass

Is something like this possible?

回答1:

You'll have to make this separate try blocks:

try:
    code a
except ExplicitException:
    pass

try:
    code b
except ExplicitException:
    try:
        code c
    except ExplicitException:
        try:
            code d
        except ExplicitException:
            pass

This assumes you want to run code c only if code b failed.

If you need to run code c regardless, you need to put the try blocks one after the other:

try:
    code a
except ExplicitException:
    pass

try:
    code b
except ExplicitException:
    pass

try:
    code c
except ExplicitException:
    pass

try:
    code d
except ExplicitException:
    pass

I'm using except ExplicitException here because it is never a good practice to blindly ignore all exceptions. You'll be ignoring MemoryError, KeyboardInterrupt and SystemExit as well otherwise, which you normally do not want to ignore or intercept without some kind of re-raise or conscious reason for handling those.

回答2:

You can use fuckit module.
Wrap your code in a function with @fuckit decorator:

@fuckit
def func():
    code a
    code b #if b fails, it should ignore, and go to c.
    code c #if c fails, go to d
    code d

回答3:

Extract (refactor) your statements. And use the magic of and and or to decide when to short-circuit.

def a():
    try: # a code
    except: pass # or raise
    else: return True

def b():
    try: # b code
    except: pass # or raise
    else: return True

def c():
    try: # c code
    except: pass # or raise
    else: return True

def d():
    try: # d code
    except: pass # or raise
    else: return True

def main():   
    try:
        a() and b() or c() or d()
    except:
        pass

回答4:

If you don't want to chain (a huge number of) try-except clauses, you may try your codes in a loop and break upon 1st success.

Example with codes which can be put into functions:

for code in (
    lambda: a / b,
    lambda: a / (b + 1),
    lambda: a / (b + 2),
    ):
    try: print(code())
    except Exception as ev: continue
    break
else:
    print("it failed: %s" % ev)

Example with arbitrary codes (statements) directly in the current scope:

for i in 2, 1, 0:
    try:
        if   i == 2: print(a / b)
        elif i == 1: print(a / (b + 1))
        elif i == 0: print(a / (b + 2))
        break        
    except Exception as ev:
        if i:
            continue
        print("it failed: %s" % ev)

来源：https://stackoverflow.com/questions/17322208/multiple-try-codes-in-one-block

标签

python

exception

exception-handling

try-catch

except