Transcript Continue on getting started

INTRODUCTION TO PYTHONGETTING STARTED (CONT)
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
>>>
CONTINUE..

For strings, it is easy to iterate over each character:
>>> foo ='abc‘
>>> for c in foo:
print c
a
b
c
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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:
BUILT-IN FUNCTIONS
Function
Description
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 preettyprinted 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)
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):
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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.
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VARIABLE ASSIGNMENT
Assignment operators (=)
anInt =-12
aString=‘cart’
aFloat =-3.1234
alist= [3.124,’ abcd’,8.82]
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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.

CONTINUE..
Example :
+= ,-=,*=, /=,%=,**= , <<=,>>=,&=,^=,|=
Thus , x = x+1  x+=1
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Python does not support pre/post increment nor pre/postdecrement 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
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'

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
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
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IDENTIFIERS-CONTINUE
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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
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BUILT-INS
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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