Flow Control

Conditional

if 5 > 3:
     print "good"
elif 3 == 3:
     print "hrm"
else:
     print "okay..."
	

Iteration

for i in 1,2,3,15,6,3,5.4,'blah':
     print i
	

outputs:

1
2
3
15
6
3
5.4
blah
	  

Miscellaneous

Python also has break, continue and else keywords defined for loops, but I won't go into detail here.

Pass

The pass statement is the 'do nothing' statement, in Python you must use this statement if you want nothing to happen, you cannot use a blank line.

Functions

Functions are defined using the def keyword:

def function():
     print "the body of the function"
	

You do not define what a function returns, this allows functions to return different things for different situations. If a function doesn't explicitly return anything, it returns the special value 'None'.

Python supports a rich set of argument definition and usage:

Default values:

def function(argument="initial value"):
	    

means that if the caller of the function does not supply a value for argument, the value "initial value" is automatically inserted.

Positional and Named parameter passing:

If a function is defined as:

	   
def function(a, b):
	    

then it can be called in two ways with the same results:

1. function("a value", "b value")
   		

2. function(b="b value", a="a value")
   		

Arbitrary number of arguments:

Python has very good support for this, but I haven't covered the data structures needed to explain this, so...