t o r _ 2 @ d e c o r a t o r _ 1 d e f f ( ) : p a s s is equivalent to: d e f f ( ) : p a s s f = d e c o r a t o r _ 1 ( f ) f = d e c o r a t o r _ 2 ( f )
" / h e l l o " ) d e f h e l l o ( ) : p a s s is equivalent to: d e c o r = r o u t e ( " / h e l l o " ) d e f h e l l o ( ) : p a s s h e l l o = d e c o r ( h e l l o ) route is not the decorator. It is a function that returns the decorator.
data types. x = 1 0 d e f s q u a r e ( x ) : r e t u r n x * x y = x f = s q u a r e > > > f ( 4 ) 1 6 > > > f < f u n c t i o n s q u a r e a t 0 x 1 0 9 e c 5 1 b 8 >
other functions. > > > d e f f s u m ( f , x , y ) : . . . r e t u r n f ( x ) + f ( y ) . . . > > > f s u m ( s q u a r e , 3 , 4 ) 2 5 > > > f s u m ( l e n , " h e l l o " , " s i n g a p o r e " ) 1 4 In fact, there are many standard library functions that take function arguments. > > > m a x ( [ " a l i c e " , " c h a r l i e " , " e v e " , d a v e " , " b o b " ] ) ' e v e ' > > > m a x ( [ " a l i c e " , " c h a r l i e " , " e v e " , d a v e " , " b o b " ] , k e y = l e n ) ' c h a r l i e '
d e f m a k e _ a d d e r ( x ) : d e f a d d ( y ) : r e t u r n x + y r e t u r n a d d a d d 5 = m a k e _ a d d e r ( 5 ) p r i n t a d d 5 ( 2 ) Output: 7
take variable number of arguments. > > > m a x ( 3 , 9 , 4 ) 9 > > > m a x ( 3 , 9 , 4 , 2 3 ) 2 3 And here is how they are written. d e f l o g ( l a b e l , * a r g s ) : f o r a i n a r g s : p r i n t l a b e l , a l o g ( " I N F O " , 1 , 2 , 3 ) Output: I N F O 1 I N F O 2 I N F O 3
> > > a r g s = [ 1 , 2 ] > > > l o g ( " I N F O " , * a r g s ) I N F O 1 I N F O 2 > > > a r g s = [ ' D E B U G ' , 1 , 2 ] > > > l o g ( * a r g s ) D E B U G 1 D E B U G 2 This can be used for any function. > > > a r g s = [ ' f f ' , 1 6 ] > > > i n t ( * a r g s ) 2 5 5 > > > i n t ( ' f f ' , 1 6 ) 2 5 5
i m e i m p o r t a s c t i m e > > > > > > a s c t i m e . _ _ n a m e _ _ ' a s c t i m e ' > > > > > > a s c t i m e . _ _ m o d u l e _ _ ' t i m e ' > > > > > > p r i n t a s c t i m e . _ _ d o c _ _ a s c t i m e ( [ t u p l e ] ) - > s t r i n g C o n v e r t a t i m e t u p l e t o a s t r i n g , e . g . ' S a t J u n 0 6 1 6 : 2 6 : 1 1 1 9 9 8 ' . W h e n t h e t i m e t u p l e i s n o t p r e s e n t , c u r r e n t t i m e a s r e t u r n e d b y l o c a l t i m e ( ) i s u s e d .
execution of this code. d e f s q u a r e ( x ) : r e t u r n x * x d e f s u m _ o f _ s q u a r e s ( x , y ) : r e t u r n s q u a r e ( x ) + s q u a r e ( y ) p r i n t s u m _ o f _ s q u a r e ( 3 , 4 )
statements. d e f s q u a r e ( x ) : p r i n t " s q u a r e " , x r e t u r n x * x d e f s u m _ o f _ s q u a r e s ( x , y ) : p r i n t " s u m _ o f _ s q u a r e s " , x , y r e t u r n s q u a r e ( x ) + s q u a r e ( y ) p r i n t s u m _ o f _ s q u a r e ( 3 , 4 ) Output: s u m _ o f _ s q u a r e s 3 4 s q u a r e 3 s q u a r e 4 2 5
those functions using a decorator. d e f t r a c e ( f ) : " " " D e c o r a t o r t o t r a c e c a l l s t o a f u n c t i o n . " " " d e f g ( * a r g s ) : p r i n t f . _ _ n a m e _ _ , a r g s v a l u e = f ( * a r g s ) p r i n t " r e t u r n " , v a l u e r e t u r n v a l u e r e t u r n g This also prints the return value along with function name.
r a c e d e f s q u a r e ( x ) : r e t u r n x * x @ t r a c e d e f s u m _ o f _ s q u a r e s ( x , y ) : r e t u r n s q u a r e ( x ) + s q u a r e ( y ) p r i n t s u m _ o f _ s q u a r e ( 3 , 4 ) Output: s u m _ o f _ s q u a r e s 3 4 s q u a r e 3 r e t u r n 9 s q u a r e 4 r e t u r n 1 6 r e t u r n 2 5 2 5
d e f s q u a r e ( x ) : " " " C o m p u t e s s q u a r e o f a n u m b e r . " " " r e t u r n x * x Lets look at function metadata: > > > s q u a r e < f u n c t i o n g a t 0 x 1 0 4 f d d 2 a 8 > > > > s q u a r e . _ _ n a m e _ _ ' g ' > > > h e l p ( s q u a r e ) H e l p o n f u n c t i o n g i n m o d u l e t r a c e : g ( * a r g s ) What happened to the function metadata?
o o l s module provides a helpers to fix that. d e f t r a c e ( f ) : " " " D e c o r a t o r t o t r a c e c a l l s t o a f u n c t i o n . " " " @ f u n c t o o l s . w r a p s ( f ) d e f g ( * a r g s ) : p r i n t f . _ _ n a m e _ _ , a r g s v a l u e = f ( * a r g s ) p r i n t " r e t u r n " , v a l u e r e t u r n v a l u e r e t u r n g
call log. l e v e l = 0 d e f l o g ( t e x t ) : i n d e n t = ' | ' * l e v e l + ' | - - ' p r i n t i n d e n t + t e x t d e f t r a c e ( f ) : d e f g ( * a r g s ) : g l o b a l l e v e l a r g s t r = ' ( ' + " , " . j o i n ( [ r e p r ( a ) f o r a i n a r g s ] ) + ' ) ' l o g ( f . _ _ n a m e _ _ + a r g s t r ) l e v e l + = 1 v a l u e = f ( * a r g s ) l o g ( " r e t u r n " + r e p r ( v a l u e ) ) l e v e l - = 1 r e t u r n v a l u e r e t u r n g
m _ o f _ s q u a r e s ( 3 , 4 ) | | - - s q u a r e ( 3 ) | | | - - r e t u r n 9 | | - - s q u a r e ( 4 ) | | | - - r e t u r n 1 6 | | - - r e t u r n 2 5 2 5
n t f i b ( 4 ) | - - f i b ( 4 ) | | - - f i b ( 3 ) | | | - - f i b ( 2 ) | | | | - - f i b ( 1 ) | | | | | - - r e t u r n 1 | | | | - - f i b ( 0 ) | | | | | - - r e t u r n 1 | | | | - - r e t u r n 2 | | | - - f i b ( 1 ) | | | | - - r e t u r n 1 | | | - - r e t u r n 3 | | - - f i b ( 2 ) | | | - - f i b ( 1 ) | | | | - - r e t u r n 1 | | | - - f i b ( 0 ) | | | | - - r e t u r n 1 | | | - - r e t u r n 2 | | - - r e t u r n 5 5
computation in our fib function? How about caching the return values? Doing this is very popular in functional programming world and it is called memoize. d e f m e m o i z e ( f ) : # c a c h e t o s t o r e t h e r e t u r n v a l u e s o f t h e f u n c t i o n c a c h e = { } d e f g ( * a r g s ) : i f a r g s n o t i n c a c h e : c a c h e [ a r g s ] = f ( * a r g s ) r e t u r n c a c h e [ a r g s ] r e t u r n g
m e m o i z e @ t r a c e d e f f i b ( n ) : i f n = = 0 o r n = = 1 : r e t u r n 1 e l s e : r e t u r n f i b ( n - 1 ) + f i b ( n - 2 ) The t r a c e is still kept to see the new execution trace after decorating with memoize.
) | - - f i b ( 4 ) | | - - f i b ( 3 ) | | | - - f i b ( 2 ) | | | | - - f i b ( 1 ) | | | | | - - r e t u r n 1 | | | | - - f i b ( 0 ) | | | | | - - r e t u r n 1 | | | | - - r e t u r n 2 | | | - - r e t u r n 3 | | - - r e t u r n 5 5
h _ r e t r i e s that continue to retry for 5 times if there is any exception raised in the function. @ w i t h _ r e t r i e s d e f w g e t ( u r l ) : r e t u r n u r l l i b 2 . u r l o p e n ( u r l ) . r e a d ( ) w g e t ( " h t t p : / / g o o g l e . c o m / n o - s u c h - p a g e " ) Should print: w g e t f a i l e d , r e t r y i n g . . . w g e t f a i l e d , r e t r y i n g . . . w g e t f a i l e d , r e t r y i n g . . . w g e t f a i l e d , r e t r y i n g . . . w g e t f a i l e d , r e t r y i n g . . . T r a c e b a c k ( m o s t r e c e n t c a l l l a s t ) : . . . u r l l i b 2 . H T T P E r r o r : H T T P E r r o r 4 0 4 : N o t F o u n d
n c t o o l s d e f w i t h _ r e t r i e s ( f ) : @ f u n c t o o l s . w r a p s ( f ) d e f g ( * a r g s ) : f o r i i n r a n g e ( 5 ) : # c a l l t h e o r i g i n a l f u n c t i o n a n d i g n o r e a n y e x c e p t i o n t r y : r e t u r n f ( * a r g s ) e x c e p t : p r i n t f . _ _ n a m e _ _ , " f a i l e d , r e t r y i n g . . . " # c a l l t h e o r i g i n a l f u n c t i o n . # t h i s t i m e , l e t t h e e x c e p t i o n g o o u t . r e t u r n f ( * a r g s ) r e t u r n g
an argument to the decorator? @ w i t h _ r e t r i e s ( n u m _ r e t r i e s = 3 ) d e f w g e t ( u r l ) : r e t u r n u r l l i b 2 . u r l o p e n ( u r l ) . r e a d ( ) even better: @ w i t h _ r e t r i e s ( n u m _ r e t r i e s = 3 , d e l a y = 0 . 1 ) d e f w g e t ( u r l ) : r e t u r n u r l l i b 2 . u r l o p e n ( u r l ) . r e a d ( )
t r i e s is not the decorator now. The return value of w i t h _ r e t r i e s is a decorator. i m p o r t f u n c t o o l s i m p o r t t i m e d e f w i t h _ r e t r i e s ( n u m _ r e t r i e s = 5 , d e l a y = 0 ) : d e f d e c o r a t o r ( f ) : @ f u n c t o o l s . w r a p s ( f ) d e f g ( * a r g s ) : f o r i i n r a n g e ( n u m _ r e t r i e s ) : t r y : r e t u r n f ( * a r g s ) e x c e p t : p r i n t " F a i l e d t o d o w n l o a d , r e t r y i n g . . . " t i m e . d e l a y ( d e l a y ) # C a l l t h e o r i g i n a l f u n c t i o n . T h i s t i m e , l e t t h e e x c e p t i o n g o o u t . r e t u r n f ( * a r g s ) r e t u r n g r e t u r n d e c o r a t o r
framework. " " " F a k e w e b f r a m e w o r k . " " " d e f r o u t e ( p a t h ) : " " " R e t u r n s a d e c o r a t o r t o r e g i s t e r m a p p i n g f r o m a p a t h t o a f u n c t i o n . " " " d e f d e c o r ( f ) : # T O D O : F I X M E p a s s r e t u r n d e c o r d e f r e q u e s t ( p a t h ) : " " " R e t u r n s t h e r e s p o n s e r e t u r n e d b y t h e w e b a p p f o r g i v e n p a t h . " " " r e t u r n " 4 0 4 - N o t F o u n d " d e f r u n ( p o r t = 8 0 8 0 ) : " " " R u n s a w e b s e r v e r t o s e r v e t h e w e b a p p . " " " p r i n t " N o t y e t i m p l e m e n t e d "
k e w e b i m p o r t r o u t e , r u n @ r o u t e ( " / h e l l o " ) d e f h e l l o ( ) : r e t u r n " H e l l o , w o r l d ! " @ r o u t e ( " / b y e " ) d e f b y e ( ) : r e t u r n " G o o d b y e ! " i f _ _ n a m e _ _ = = " _ _ m a i n _ _ " : r u n ( )
t w e b a p p t o l o a d t h e m a p p i n g i m p o r t w e b a p p f r o m f a k e w e b i m p o r t r e q u e s t i f _ _ n a m e _ _ = = " _ _ m a i n _ _ " : p r i n t r e q u e s t ( " / h e l l o " ) p r i n t r e q u e s t ( " / b y e " ) p r i n t r e q u e s t ( " / n o - s u c h - p a g e " ) Output: 4 0 4 - N o t F o u n d 4 0 4 - N o t F o u n d 4 0 4 - N o t F o u n d
= [ ] d e f r o u t e ( p a t h ) : d e f d e c o r ( f ) : _ r o u t e s . a p p e n d ( ( p a t h , f ) ) r e t u r n f r e t u r n d e c o r d e f r e q u e s t ( p a t h ) : f o r _ p a t h , f u n c i n _ r o u t e s : i f _ p a t h = = p a t h : r e t u r n f u n c ( ) r e t u r n " 4 0 4 - N o t F o u n d "
f u n c ( e n v , s t a r t _ r e s p o n s e ) : p a t h = e n v [ ' P A T H _ I N F O ' ] s t a r t _ r e s p o n s e ( ' 2 0 0 O K ' , [ ( " C o n t e n t - t y p e " , " t e x t / p l a i n " ) ] ) r e t u r n r e q u e s t ( p a t h ) d e f r u n ( p o r t = 8 0 8 0 ) : f r o m w s g i r e f . s i m p l e _ s e r v e r i m p o r t m a k e _ s e r v e r s e r v e r = m a k e _ s e r v e r ( " l o c a l h o s t " , p o r t , w s g i f u n c ) p r i n t " h t t p : / / l o c a l h o s t : { } / " . f o r m a t ( p o r t ) s e r v e r . s e r v e _ f o r e v e r ( )
h o n w e b a p p . p y h t t p : / / l o c a l h o s t : 8 0 8 0 / Lets try visiting the URLs. $ c u r l h t t p : / / l o c a l h o s t : 8 0 8 0 / h e l l o H e l l o , w o r l d ! $ c u r l h t t p : / / l o c a l h o s t : 8 0 8 0 / b y e G o o d b y e ! $ c u r l h t t p : / / l o c a l h o s t : 8 0 8 0 / n o - s u c h - p a g e 4 0 4 - N o t F o u n d
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