Why can't Python decorators be chained across definitions? -

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why arn't following 2 scripts equivalent?

(taken question: understanding python decorators)

def makebold(fn):     def wrapped():         return "<b>" + fn() + "</b>"     return wrapped  def makeitalic(fn):     def wrapped():         return "<i>" + fn() + "</i>"     return wrapped  @makebold @makeitalic def hello():     return "hello world"  print hello() ## returns <b><i>hello world</i></b>

and decorated decorator:

def makebold(fn):     def wrapped():         return "<b>" + fn() + "</b>"     return wrapped  @makebold def makeitalic(fn):     def wrapped():         return "<i>" + fn() + "</i>"     return wrapped  @makeitalic def hello():     return "hello world"  print hello() ## typeerror: wrapped() takes no arguments (1 given)

why want know? i've written retry decorator catch mysqldb exceptions - if exception transient (e.g. timeout) re-call function after sleeping bit.

i've got modifies_db decorator takes care of cache-related housekeeping. modifies_db decorated retry, assumed functions decorated modifies_db retry implicitly. did go wrong?

the problem second example that

@makebold def makeitalic(fn):     def wrapped():         return "<i>" + fn() + "</i>"     return wrapped

is trying decorate makeitalic, decorator, , not wrapped, function returns.

you can think intend this:

def makeitalic(fn):     @makebold     def wrapped():         return "<i>" + fn() + "</i>"     return wrapped

here makeitalic uses makebold decorate wrapped.


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