I'm not familiar with python either,  following if should only be for   print("-")  and not print(i) . and i assume, end=' ' is for not adding line break.
if (i !=1)  
          print("-")

N = int(input("N: "))
i=1
Sum=0

while i <= N:
    
    if i%2==0:   
          if (i !=1):
               print("-")                                          #If i is even
           print(i)
           
 
           Sum=Sum-i
    else:    
          if (i !=1): 
               print("+")                                               #if i is odd
           print(i)
           Sum=Sum+i
    i=i+1
    
print("=", Sum)  

probably that would work, pls add end = ' ' to all the print statement