pythons基础学习-4

模块引用， 一个py文件可以做一个模块， 通过__name__控制主块是否运行

if __name__ == '__main__':
    print 'This program is being run by itself'
else:
    print 'I am being imported from another module'

dir函数 列举模块的标识符(变量、函数、类等)



数据结构：
list使用中括号包含，逗号分隔    a = [1, 2, 3, 4, 5]  可以改变
元组使用圆括号包含，逗号分隔 b = (1, 2,3, 4)  不可改变


list的操作

#!C:\Python33
shoplist = ['apple', 'mango', 'carrot', 'banana']

for item in shoplist:
    print (item)

shoplist.append('rice')

print('================')
for item in shoplist:
    print (item)

print('================')
shoplist.sort()
for item in shoplist:
    print (item)

print('================')
del shoplist[1:3]
for item in shoplist:
    print (item)

结果

>>>
apple
mango
carrot
banana
================
apple
mango
carrot
banana
rice
================
apple
banana
carrot
mango
rice
================
apple
mango
rice
>>>

元组输出：

age = 22
name = 'name'

print ('%s is %d years old' % (name, age))
print ('Why is %s playing with that python?' % name )

结果：


>>>
name is 22 years old
Why is name playing with that python?
>>>

注意 格式化输出 中间没有逗号

字典 键/值对用冒号分割，而各个对用逗号分割，所有这些都包括在花括号中。

#!C:\Python33
a = {1:'one', 2:'two'}

print('=======================')

for i,st in a.items():
    print(" %d : %s" %(i, st))


print('=======================')

a[3] = 'three'
a[4] = 'four'
for i,st in a.items():
    print(" %d : %s" %(i, st))

print('=======================')

del a[3]
for i,st in a.items():
    print(" %d : %s" %(i, st))

结果：
=======================
 1 : one
 2 : two
=======================
 1 : one
 2 : two
 3 : three
 4 : four
=======================
 1 : one
 2 : two
 4 : four
>>>

参考 -- 列表，元组， 如果直接赋值则使用同一个对象， 否则需要使用切片操作获取新对象

#!C:\Python33
a = ['one', 'two', 'three', 'fourth']
b = a
c = a[1:2]
del a[1]

print('=========b==============')

for i in b:
    print(i)

print('==========c=============')

for st in c:
    print("%s" %st)
结果：
>>>
=========b==============
one
three
fourth
==========c=============
two
>>>