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