Introduction to python-getting started (cont)

1. Introduction to python-getting started (cont)

2. Continue.. >>> for eachnum in [0,1,2]: print eachnum 0 1 2 • 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 0 1 2 >>>

3. Continue.. • 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:

4. Built-in functions

5. Statements 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):

6. Multiple 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.

7. Variable assignment • Assignment operators (=) anInt =-12 aString=‘cart’ aFloat =-3.1234 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.

8. Continue.. 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

9. Continue.. • “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'

10. Continue.. • ‘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

11. 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

12. Identifiers-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

13. Built-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