Definition_of_if_statement

#The following code is used by the instructor to demonstrate how /if/ functions:

def absolute(x):
    if x < 0:   # if x < 0 is True, then execute line 5, i.e. x = -x
        x = -x
    return x    # this line is executed whether or not line 4 is True or False

print absolute(-3)
#>>>3 (the '#>>>' indicates the actual output of in code editor)
print absolute(4)
#>>>4

#Following this logic, I wrote a procedure that compares two parameters and returns bigger one, 
#shown below #version_1:

#CLARIFICATION by Johanne: the logic in the above code applies only when /else/ is not present 
#before /return x/ (line 6)

#version_1
def bigger (a,b):
    if a > b:
        b = a
    return b
print bigger(2,7)
#>>>7
print bigger(3,2)
#>>>3
print bigger(3,3)
#>>>3

#This procedure seems OK, printing out correct answers. But in the lecture, the instructor 
#suggested two other versions, which seem to contradict my understanding of the use of /if/,
#as shown in the following code:

#version_2 
def bigger(a,b):
    if a > b:
        return a
    return b
print bigger(2,7)
#>>>7
print bigger(3,2)
#>>>3
print bigger(3,3)
#>>>3

#The rationale behind the first two procedures predicts that #version_2 should return 2 values, 
#i.e. both line 38 and line 39 will be executed, contrary to the actual output.

#CLARIFICATION by Johanne: one function can only have one return.
#version_3
def bigger(a,b):
    if a > b:
        r = a
    else:
        r =  b
    return r
print bigger(2,7)
#>>>7
print bigger(3,2)
#>>>3
print bigger(3,3)
#>>>3

#CLARIFICATION by Johanne: if /else/ is present, then only one of line 54 and line 56 will be
#executed.

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