python-小知识点-14

'''
python2 python3

'''
#python2
print()  print 'abc'
range()   xrange() 生成器
raw_input()

#python3
print('abc')
range()
input()

# = 赋值 == 比较值是否相等   is 比较，比较的是内存地址  id(内容)
li1 = [1,2,3]
li2 = li1
li3 = li2
print(id(li1),id(li2))

>>> li1 = [1,2,3]
>>> li2 = li1
>>> li3 = li2
>>> print(id(li1),id(li2))
6120008 6120008
>>> li3 = 3
>>> print(id(li1),id(li2))
6120008 6120008
>>> print(li2)
[1, 2, 3]
>>> print(li3)
3
>>> print(id(li1),id(li3))
6120008 8791266881344
>>> li2 = 5
>>> li1
[1, 2, 3]
>>> print(id(li1),id(li2))
6120008 8791266881408
>>>

#数字，字符串 小数据池
#数字的范围 -5 -- 256
#字符串：1，不能有特殊字符
#        2，s*20 还是同一个地址，s*21以后都是两个地址  #自己试试
i1 = 6
i2 = 6
print(id(i1),id(i2)) # 8791266881440 8791266881440 共用一个地址
i1 = 300
i2 = 300
print(id(i1),id(i2)) # 6338640 5916688 不共用

s1 = 'alex'
s2 = 'alex'
print(si is s2) #True

s1 = '@alex'
s2 = '@alex'
print(si is s2) #False

#剩下的 list dict tuple set
l1 = [1,]
l2 = [1,]
print(l1 is l2) #False

s = 'alex'
s1 = b'alex'
print(s,type(s))
print(s1,type(s1))

s = '中国'
print(s,type(s))
s1 = b'中国'
print(s1,type(s1))

s1 = 'alex'
# encode 编码，如何将str --> bytes, ()
s11 = s1.encode('utf-8')
s11 = s1.encode('gbk')
print(s11)
s2 = '中国'
s22 = s2.encode('utf-8')
s22 = s2.encode('gbk')
print(s22)