Python参考手册----第一章： Python简介（一）

一、Python简介

1.1 print "Hello World"

1.2 变量和算术表达式

#print

principal = 1000

rate = 0.05

numyears = 5

year = 1



while year <= numyears:

    principal = principal * (1 + rate)



    print year, principal 

#    print(year, principal)



    print "%3d %0.2f" % (year, principal)

#    print("%3d %0.2f" % (year, principal))



    print format(year,"3d"), format(principal, "0.2f")

#    print(format(year,"3d"), format(principal,"0.2f"))



    print "{0:3d} {1:0.2f}".format(year,principal)

#    print("{0:3d} {1:0.2f}".format(year,principal))



    year += 1

#同一行上用分号隔开多条语句 
#循环主体由缩进表示，每个缩进层次使用4个空格 
#格式化字符序列 
#%3d将一个整数格式化为在一个宽度为3的列中右对齐
 1.3条件语句

a = 1

b = 2



if a < b:

    print "Computer says yes"

else:

    print "Computer syas no"



if a < b:

    pass # Do nothing

else:

    print "Computer syas no"

    



# or and not 

product = "game"

type1 = "pirate memory"

age = 9



if product == "game" and type1 == "pirate memory" \

                     and not (age < 4 or age > 8):

    print "I will take it!"

else:

    print "no...."

    

    

#switch case 



suffix = ".html"

if suffix == ".html":

    content = "text/html"

elif suffix == ".jpg":

    content = "image/jpeg"

elif suffix == ".png":

    content = "image/png"

else:

    raise RuntimeError("Unknown content type")

print content



#True False



s = 'p'



if 'spam' in s:

    has_spam = True

else:

    has_spam = False

    

print has_spam



has_spam = "spam" in s



print has_spam