python:practice set copy

content will be learn:

how to use set.

set is a object ,characters :not be repetitive,can be hashing.

startup in two way :

set () can be add and delete

frozenset()  can not be change,not be update and remove

set () :use to intersection,union set ,aperation to achieve our goal

a=set('suny)

a.add('go‘）。old set ,have four elements:'s','u','n','y'

                       renew set :have five elements:'s','u;,'n','y','go'

a.update('go').old set  hvae four elements:'s',;u;,'n;,;y;

                       renew set have six elements:'s;'u','n','y','g','o'

remove,del  

set() operation characters:

in ,not in  == != :return Boole value 'True' 'False'

,subset (subaggregate subcollection)superset: can use to remove duplicates.de-weight.

calling set () :

for i in set():

print(i)

subset(subaggregate,subcollection),operation characters

set()>set()

set() in set()

combin two more set().can use operate union() or  

union and or is equivalent.

operation characters:

set() | set()

s1.union(s2)

intersection:

operation characters:

set()&set()

s1 . intersection(s2)

check set :

operation characters:

difference

s3=s1-s2

s1 . difference(s2)

symmetric difference set()

operation characters:

s3=s1^s2

s1 . symmetric.difference(se)

subroutine,subaggregate

function parameters:

category:

form parameters； for example.   def     function(a,). this way  'a' is a form parameters.

actual parameters(actual argument):   function(1,2).this '1,2' is actual parameters.

default parameters:   instance:  def  function( sexuality='male')  this 'sexuality' is default.

uncertain parameters:   def function (*args)  this ' *args' is uncertain parameters.

                                                                  can be  assignment(evaluation,valuation)

*args can be assignment unnamed parameters  or untitled parameters. for example  19  'male'

def function (*args)

a=[1,2,3]

function(a) express for ([1,2,3],)

function(*a) express for (1,2,3)

if function (*[1,2,3} show for [1,2,3] same  to function assignment list

**args can be assignment named parameters.or titled parameters. for example  name=' alan'

def function(**kwargs):

a={}

function(**a) can express for {   }

placeholder:

placeholder characters: %s   usage:  print(' you can go to %s'% parameters)

                                                                                                 the position have many parameters can express as " go to  %s,%s"%(parameter,parameter)

formal parameters and actual parameters corresponding relation:  one position  formal parameter  corresponding  one actual parameter.