Python - funciones y estructuras de repetición

Expresion=Signo=""

Num=int(input("Numero: "))

for Cont in range(Num):

    Expresion+=Signo+str((10+Cont))

    Signo="+" if Signo=="-" else "-"

print("f3("+str(Num)+")="+Expresion +"="+ str(eval(Expresion)))

def f3(Num):

    return (sum([(10+N)*1 if N%2==0 else (10+N)*-1 for N in range(Num)]))

print(f3(int(input("Numero: "))))

def f3(Num):

    Expresion=Signo=""

    for Cont in range(Num):

        Expresion+=Signo+str((10+Cont))

        Signo="+" if Signo=="-" else "-"

    return "f3("+str(Num)+")="+Expresion +"="+ str(eval(Expresion))

print(f3(int(input("Numero: "))))

print((sum([(10+N) if N%2==0 else (10+N)*-1 for N in range(int(input("Numero: ")))])))

def funcion_f3(num):

  result = 0

  for n in range(num):

    result += - (start + n) if n % 2 else start + n

  return result

print(funcion_f3(3)) # 11

print(funcion_f3(1)) # 10

print(funcion_f3(2)) # -1