#!/usr/bin/env python
# Several wrong versions of introductory python code, with explanations

# Version 1:
for n in range(5):
    sum += n
print("Total sum = " + sum)
# BUT: there is no += in Python

# Version 2:
for n in range(5):
    sum = sum + n
print("Total sum = " + sum)
# BUT: sum is a builtin fct, so can't be used as variable

# Version 3:
global s
for n in range(5):
    s = s + n
print("Total sum = " + s)
# BUT: you don't need to declare a variable, to make it known, just assign to it

# Version 4:
s = 0
for n in range(5):
    s = s + n
print("Total sum = " + s)
# BUT: printing fails because you can't append ('+') a string with an int

# Version 5
# compute the sum over the first 5 integer numbers
s = 0
for n in range(5):
    s = s + n
print("Total sum = ")
print(s)
# BUT: this is the wrong result!!

# Version 6
# compute the sum over the first 5 integer numbers
s = 0
for n in range(5):
    s = s + n
print("Total sum = " + str(s))
print(s)
# NB: str(s) turns the int value into a string

# Version 7 (final)
s = 0
for n in range(6):
    s = s + n
print("Total sum = ")
print(s)
# finally, this is the correct code