python - Trying to use variables outside of a for loop gives a SyntaxError: no binding for nonlocal 'max_' found -

def min_diff(arry_):    max_ =0    temp_ =0    in arry_:      nonlocal max_      nonlocal temp_      if > max_:         nonlocal max_         nonlocal temp_         temp_ = max_         max_ =i    return max_-temp_ 

i want use max_ , temp_ outside loop getting error

syntaxerror: no binding nonlocal 'max_' found 

nonlocal can applied in functions have nested scope. nested scope when define function inside of function.

python doesn't have block scopes; for loop doesn't create new scope, don't need use nonlocal in loop. variables available throughout rest of function. drop nonlocal statements altogether:

def min_diff(arry_):     max_ = 0     temp_ = 0     in arry_:         if > max_:             temp_ = max_             max_ =     return max_ - temp_ 

in python, functions, class definitions , comprehensions (list, set, , dict comprehensions generator expressions) own scope, , functions can act parent scope closures (nonlocal variables).

there bug in code; if pass in list first value maximum value in list, temp_ set 0 , never changes. won't ever find second-highest value in case, because first i if > max_: true. you'd need test if i greater temp_ in case:

def min_diff(arry_):     max_ = 0     temp_ = 0     in arry_:         if > max_:             temp_ = max_             max_ =         elif > temp_:             temp_ =     return max_ - temp_ 

as side note: don't need use trailing underscores in local variables. of local names used, max_ potentially shadow built-in max() function, since don't use function @ all, using max_ instead of max in function not requirement. i'd drop trailing _ underscores names in function. i'd use different names; perhaps highest , secondhighest.

last not least, use heapq.nlargest() function 2 largest values, efficiently:

from heapq import nlargest  def min_diff(values):     highest, secondhighest = nlargest(2, values)     return highest - secondhighest 

you may want add length checks there; if len(values) < 2 true, should happen instead?