Python Statements

Assignment

As in C/C++, the = is the assignment operator.

Assignments create object references. References are like pointers.
Names are created when first assigned.
Names must be assigned before being referenced.
Implicit assignments: import, from , def, class, for, function args, etc.

Three forms of the assignment statement:

Operation	Interpretation
init_velocity = 14.5	Basic form. Object 14.5 is created. init_velocity refers to it.
last, first = 'Schwartz', 'Andrew'	Tuple assignment.
[part_name, part_no] = "widget", 23654	List assignment.
x = y = 0	Multiple target. Note, that only one object is created!

Variable Names

Start with a letter or underscore; followed by any number of letters, digits, and underscores.
Variable names are case sensitive.
Reserved Words May Not Be Used as Variable Names

Python Reserved Words

and	assert	break	class
continue	def	del	elif
else	except	exec	finally
for	from	global	if
import	in	is	lambda
not	or	pass	print
raise	return	try	while

Statements

General Rules for Statements:

Statements may be arbitrarily long.
Statements may span lines if you're continuing an open syntactic pair, e.g., if parentheses are open.
Statements may span lines if they end in a backslash. (Backslash escapes the newline.)
Statements on contiguous lines with the same indentation form a block.
Lines that end in a colon ( : ) must be followed by an indented block.
Do not mix tabs with spaces for indentation. It is best to use only spaces for indentation.

print

Statement	Explanation
print "comfy", "chair"	Print items from tuple, space separated, and newline.
print "penguin",	Final comma suppresses newline.
print "%d penguins, and %d albatross." % (penguin_ct, albatross_ct)	Formatted output

if

Note that the tests in an if statement do not require enclosing parentheses.

Syntax:

if <test1>:	#if test
<statements>	#Block indentation is significant!
elif <test2>:	#Optional elif's
<statements>	#Block is delimited by indentation!
else:	#Optional else
<statements>	#Indent with spaces only!

while

Syntax:

while <test>:	#loop test
<statements>	#block for loop body
else:	#Optional else
<statements>	#else block is executed only if loop terminates normally.

Auxiliary Loop Statements

break

Terminates a loop, skipping any else block.

continue

Transfers control to the next iteration of the (innermost) loop body. The loop test is not skipped.

for

The for loop iterates through a sequence. The sequence may be a string, tuple, list, or any new object you create that responds to the sequence indexing operation.

Syntax:

for <index> in <object>:	#object items are iteratively assigned to index.
<statements>	#block for loop body
else:	#Optional else
<statements>	#else block is executed only if loop terminates normally.

To make a counting loop, you can use the built-in range( ) function to create a list of the numbers you want to count. The following example prints the integers from zero to nine:

for i in range(10):

print i,

pass

The null statement.

Python Statements

Assignment

Three forms of the assignment statement:

Variable Names

Python Reserved Words

Statements

General Rules for Statements:

print

if

while

Auxiliary Loop Statements

break

continue

for

pass

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