Python failing to recognize the number of arguments of my function

Question

Here is a strange behaviour I encountered today running a script in Python 2.7 :

Code 1 :

def pprint_compare_titles (self, ts_numbers = [1], **kwargs ) :
    temp = self.compare_titles ( ts_numbers, **kwargs )
    length = [ len( max( temp[0].keys(), key = len ) ) ]
    def temp_fun ( x, i ) :
        try :
            return self.ts[ts_numbers[i]].titles[x[0]]
        except IndexError :
            return ''
    for i in range( 0, len( temp ) ) :
        length.append( temp_fun( max( temp[i].values(),
            key = lambda x : len( temp_fun( x, i ) ) ) ) )
    for k in temp[0].keys() :
        print( '| {t: <{l}} |'.format( t = k, l = length[0] )
        + ''.join([ ' {t: <{l}} |'.format(
            t = temp_fun( temp[i][k], i ),
            l = length[i+1] )
            for i in range( 0, len(temp) ) ]) )

Output :

     45         for i in range( 0, len( temp ) ) :
     46             length.append( temp_fun( max( temp[i].values(),
---> 47                 key = lambda x : len( temp_fun( x, i ) ) ) ) )
     48         for k in temp[0].keys() :
     49             print( '| {t: <{l}} |'.format( t = k, l = length[0] )

TypeError: temp_fun() takes exactly 2 arguments (1 given)

Code 2 :

def pprint_compare_titles (self, ts_numbers = [1], **kwargs ) :
    temp = self.compare_titles ( ts_numbers, **kwargs )
    length = [ len( max( temp[0].keys(), key = len ) ) ]
    def temp_fun ( x, i ) :
        try :
            return self.ts[ts_numbers[i]].titles[x[0]]
        except IndexError :
            return ''
    for i in range( 0, len( temp ) ) :
        length.append( temp_fun( max( temp[i].values(),
            key = lambda x : len( temp_fun( x, i, 42 ) ) ) ) )
    for k in temp[0].keys() :
        print( '| {t: <{l}} |'.format( t = k, l = length[0] )
        + ''.join([ ' {t: <{l}} |'.format(
            t = temp_fun( temp[i][k], i ),
            l = length[i+1] )
            for i in range( 0, len(temp) ) ]) )

Output :

     45         for i in range( 0, len( temp ) ) :
     46             length.append( temp_fun( max( temp[i].values(),
---> 47                 key = lambda x : len( temp_fun( x, i, 42 ) ) ) ) )
     48         for k in temp[0].keys() :
     49             print( '| {t: <{l}} |'.format( t = k, l = length[0] )

TypeError: temp_fun() takes exactly 2 arguments (3 given)

The only difference between these two blocks is the number of arguments I give to temp_fun . The second output makes sens but I can't understand the behaviour of the first one, given that Python recognizes 3 parameters on the second.

If anyone has an idea of what is going on, I would gladly take it.

Answer 1

Looks like the error is actually occurring on the line previous to that one:

    length.append( temp_fun( max( temp[i].values(),
                  #^^^^^^^^ here
        key = lambda x : len( temp_fun( x, i ) ) ) ) )

The temp_fun inside your len call has the correct number of arguments, but not the temp_fun inside your append call.