Day 3 , I will introduce fucntion, if-statement, for, while and module. Yes after the day, we can coding for something. Luckly, there are not difficult, Let's go function:     named for piece of code, is like viriable named string or intger     function can accept parameter, is like your script accept argv     function can create smaller script note:     def beginning     function name is consist of underscore and character     function should follw a ()     whether () have parameter, if multi parameters should split by comma     should have repeate parameter     function should have end :     content of function should have 4 tab indent     dedent means the function is over call function:     take function name     function should follw a ()     whether '( 'have parameter, if multi parameters should split by comma     the end should be ')'

[root@alicia python_zed]# vi ex21.py  1 # function can return a value for the other useage  2   3 def add(a,b):  4   5     print "ADDING %d + %d" %(a,b)  6   7     return a+b  8   9 def subtract (a, b): 10  11     print "SUBTRACTING %d - %d" %(a,b) 12  13     return a-b 14  15 def multiply (a, b ): 16  17     print "MULTIPLYING %d * %d" % (a,b) 18  19     return a*b 20  21 def divide(a,b): 22  23     print "DIVIDING %d / %d" %(a,b) 24  25     return a/b 26  27 print "Let's do some math with just function!" 28  29 age = add(30,5) 30  31 height = subtract(78,4) 32  33 weight = multiply(90,2) 34  35 iq = divide(100,2) 36  37 print "Age: %d, Height: %d, Weight: %d, IQ: %d" %(age, height,weight,iq) 38  39 # A puzzle for the extra credit, type it in anyway 40  41 print "Here is puzzle." 42  43 what = add(age,subtract(height,multiply(weight,divide(iq,2)))) 44 #what = add(35,subtract(74,multiply(180,devide(50,2)))) 45 #what = 35+(74-180*50/2) 46  47 print "That becomes: ",what, "can you do it by hand?"----------------------------------------------------------------------[root@alicia python_zed]# python ex21.pyLet's do some math with just function!ADDING 30 + 5SUBTRACTING 78 - 4MULTIPLYING 90 * 2DIVIDING 100 / 2Age: 35, Height: 74, Weight: 180, IQ: 50Here is puzzle.DIVIDING 50 / 2MULTIPLYING 180 * 25SUBTRACTING 74 - 4500ADDING 35 + -4426That becomes:  -4391 can you do it by hand?-------------------------------------------------------------

def func(): and retrun a value for the other useage

module:

[root@alicia python_zed]# vi ex25.py 33 def sort_sentence(sentence): 34  35     """Takes in a full sentence and returns the sorted words.""" 36  37     words = break_words(sentence) 38  39     return sort_words(words) 40  41 def print_first_and_last(sentence): 42  43     """prints the first and last words of the sentence.""" 44  45     words = break_words(sentence) 46  47     print_first_word(words) 48  49     print_last_word(words) 50  51 def print_first_and_last_sorted(sentence): 52  53     """sorts the words the print the first and last words""" 54  55     words = sort_sentence(sentence) 56  57     print_first_word(words) 58  59     print_last_word(words) 60 "ex25.py" 60L, 969C                                           60,1-4   -------------------------------------------------------------------     >>> import ex25>>> sentence = "All good things come to those who wait.">>> words = ex25.break_words(sentence)>>> words['All', 'good', 'things', 'come', 'to', 'those', 'who', 'wait.']>>> sorted_words = ex25.sort_words(words)>>> ex25.print_first_word(sorted_words)All>>> ex25.print_last_word(sorted_words) who>>> sorted_words['come', 'good', 'things', 'those', 'to', 'wait.']>>> sorted_words= ex25.sort_sentence(sentence)>>> sorted_words['All', 'come', 'good', 'things', 'those', 'to', 'wait.', 'who']>>> ex25.print_first_and_last(setence)Traceback (most recent call last):  File "
    
     ", line 1, in 
     
      NameError: name 'setence' is not defined>>> ex25.print_first_and_last(sentence)Allwait.>>> ex25.print_first_and_last_sorted(sentence)Allwho
     
    

if-statement: every if-statement must have an else if this else should never run because it doesn't make sense. then you must use a die function in the else that prints out an error message and dies never nest if-statement more than two deep and always try to do them one deep if ,elif ,else like a paragraphs, where each if-elif-else grouping is like a set of sentence, put blank lines before and after your boolean tests should have be simple, if they are very complex,you should put them into a variable

[root@alicia python_zed]# vi ex30.py  1 # else and if   2   3 people = 30  4   5 cars = 40  6   7 buses = 15  8   9 if cars > people: 10  11     print "we should take the cars." 12  13 elif cars < people: 14  15     print "we shouldn't take the cars." 16  17 else: 18  19     print "we can't decide." 20  21 if people > buses: 22  23     print "Alright, let's just take the buses." 24  25 else: 26  27     print "Fine, let's stay home then." 28  29 if cars > people and buses < cars: 30  31     print "we should take cars rather than buses.""ex30.py" 32L, 398C written    ------------------------------------------------------------------                               [root@alicia python_zed]# python ex30.pywe should take the cars.Alright, let's just take the buses.we should take cars rather than buses.

for-loop:

while use while loop only to loop forever, and that means probably. use a for-loop for all other kinds of looping, especially if there is a fixed or limited number of things to loopover debug do not use a debug, it almost have no useage the best way to debug a program is to use print, to print out the values of variable at points in the program to see where they go wrong make sure parts of your programs work as you work on them, Do not write massive files of code before you try to run them, code a little ,run a little,and fix a little

[]root@alicia python_zed]#vi ex32.py  1 # for-loop and list  2   3 the_count = [1,2,3,4,5]  4   5 fruits = ['apples', 'oranges', 'pears', 'apricots']  6   7 change = [1, 'pennies', 2, 'dimes', 3, 'quarter']  8   9 #the first kind of for-loop goes through a list 10  11 for number in the_count: 12  13     print "This is count %d " % number 14  15 # same as above 16  17 for fruit in fruits: 18  19     print "A fruit of type: %s " % fruit 20  21 # also we can go through mixed lists too 22  23 # notice we have to use %r since we don't know what's in it 24  25 for i in change: 26  27     print "I got %r " % i 28  29  30 # we can also build lists, first start with an empty one  31  32 elements = [] 33  34 # then use the range function to do 0 to 5 counts 35  36 for i in range(0,6): 37  38     print "Adding %d to the list."  %i 39  40     elements.append(i) 41  42 # now we can print them out too 43  44 for i in elements: 45  46     print "Element was: %d " % i 47  48  49 # one sentence for value to elements 50  51 elements = range(6,10) 52  53 for i in elements: 54  55     print "Elements was : %d" %i-----------------------------------------------------------------[root@huan python_zed]# python ex32.pyThis is count 1 This is count 2 This is count 3 This is count 4 This is count 5 A fruit of type: apples A fruit of type: oranges A fruit of type: pears A fruit of type: apricots I got 1 I got 'pennies' I got 2 I got 'dimes' I got 3 I got 'quarter' Adding 0 to the list.Adding 1 to the list.Adding 2 to the list.Adding 3 to the list.Adding 4 to the list.Adding 5 to the list.Element was: 0 Element was: 1 Element was: 2 Element was: 3 Element was: 4 Element was: 5 Elements was : 6Elements was : 7Elements was : 8Elements was : 9>>> help(range)Help on built-in function range in module __builtin__:range(...)    range(stop) -> list of integers    range(start, stop[, step]) -> list of integers        Return a list containing an arithmetic progression of integers.    range(i, j) returns [i, i+1, i+2, ..., j-1]; start (!) defaults to 0.    When step is given, it specifies the increment (or decrement).    For example, range(4) returns [0, 1, 2, 3].  The end point is omitted!    These are exactly the valid indices for a list of 4 elements.

ok, today's content is very much,  and we go to the lesson 35.

next, list, string, dictionary will come on.