I NTRODUCTION TO PYTHON - GETTING STARTED ( CONT )

C ONTINUE.. >>> for eachnum in [0,1,2]: print eachnum Eachnum contains the integer value. Python provides the range ( ) built-in function to generate such a list Example: >>> for eachnum in range (3): print eachnum >>>

C ONTINUE.. For strings, it is easy to iterate over each character: >>> foo ='abc‘ >>> for c in foo: print c a b c The range ( ) function has been often seen with len ( ) for indexing into a string. Example: >>> foo='abc' >>> for i in range (len(foo)): print foo[i],'(%d)'%i a (0) b (1) c (2) Display both elements and their corresponding index value:

B UILT - IN FUNCTIONS FunctionDescription dir([obj])Display attributes of object or the names of global variables if no parameter given. help([obj])Display object’s documentation string in a preetty- printed format or enters interactive help if no parameter given int (obj)Convert object to an integer len (obj)Return length of object open(fn,mode)Open file fn with mode ‘r’=read, ‘w’=write Range([start,]stop[,s tep]) Return a list of integers that begin at start up to but not including stop in increments of step; start defaults to 0 and step defaults to 1 raw_input(str)Wait for text input from the user; optional prompt string can be provided str(obj)Convert object to a string type (obj)Return type of object ( a type object itself)

S TATEMENTS AND SYNTAX Python statements are in general delimited by NEWLINEs- means one statement per line. Single statements can be broken up into multiple lines by using the backslash (\). Placed the (\) before a NEWLINE to continue the current statement onto the next line. >>> #check condition >>> if (weather_is_hot ==1) and \ (shark_warning_==0):

M ULTIPLE STATEMENTS GROUPS AS SUITES (:) Groups of individual statements making up a single code block are called “suites” in Python. Compound /complex statements such as if, while are those require a header line and a suite. Header line begin the statement (with the keyword and terminate with a colon (:), and are followed by one /more lines that make up the suite. A combination of a header line and a suite as a clause.

V ARIABLE ASSIGNMENT Assignment operators (=) anInt =-12 aString=‘cart’ aFloat = alist= [3.124,’ abcd’,8.82] Augmented assignment The equal sign can be combined with an arithmetic operation and the resulting value reassigned to the existing variable. Augmented assignment refer to the use of operators, which imply both an arithmetic operation as well as assignments.

C ONTINUE.. Example : +=,-=,*=, /=,%=,**=, >=,&=,^=,|= Thus, x = x+1  x+=1 Python does not support pre/post increment nor pre/post- decrement such as x++, --x Multiple assignment It is possible to assign multiple objects to multiple variables Example: >>> x=y=z=1 >>> x 1 >>> y 1 >>> z 1

C ONTINUE.. “Multuple “assignment –an alternative way to assign multiple variables. Not an official python term, used it because when assigning variables this way, the objects on both sides of the equal sign are tuples, a python standard type. Example: >>> x,y,z =1,2,'a string' >>> x 1 >>> y 2 >>> z 'a string'

C ONTINUE.. ‘multuple” assignments, not required a temporary variable to swap the values of two variables. Example: >>> #swapping variables in Python >>> x,y =1,2 >>> x 1 >>> y 2 >>> x,y=y,x >>> x 2 >>> y 1

IDENTIFIERS Are the set of valid strings that are allowed as name in a computer language. In here, there are keywords -names that form a construct of the language It is a reserved words that may not be used for any other purpose. Example : and, as, 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, with, yield, none

I DENTIFIERS - CONTINUE The rules for Python identifiers are as follow: First character must be letter or underscore (_) Any additional character can be alphanumeric or underscore Case sensitive : CASE != Case

B UILT - INS Built-ins- python additional set of identifiers, it is not a reserved words but it is not recommended to use since it is treated as “reserved for the system” It is a member of the _builtins_module