My first day in Python and get confused with a very short example. Hope anyone can provide some explanation about why there is some difference between these several versions. Please!
a, b = 0, 1
while b < 10:
print(b)
a, b = b, a+b
a, b = 0, 1
while b < 10:
print(b)
a = b
b = a+b
In the first version, the right hand is evaluated first, so b hasn't been incremented when you add it.
To step through the first version for a couple iterations:
1.
a = 0
b = 1
a, b = 1, 1 # b is 1, and a is 0
2.
a = 1
b = 1
a, b = 1, 2 # b is 1 and a is 1
3.
a = 1
b = 2
a, b = 2, 3 # b is 2 and a is 1
In the second version, b is assigned before you add it, so here's how the second version goes:
1.
a = 0
b = 1
a = b # a is now 1.
b = a + b # b is now 2, because both a and b are 1.
2.
a = 1
b = 2
a = b # a is now 2.
b = a + b # b is now 4, because both a and b are 2.
