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Python的数值和字符串
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Python数据类型
1。数值 --类型： 1/整型
2/长整型
3/浮点型 -- 0.0, 12.0, -18.8, 3e+7等
4/复数型 -- complex
In []: 0x34al
Out[]: 842L --0x34a --表示16进制
--l --表示长整型
In []: 4e+
Out[]: 40000000.0 In []: type(4e+)
Out[]: float --科学计数法
In []: b = "hello\nlulu"
In []: b
Out[]: 'hello\nlulu' In []: print b
hello
lulu --里面有换行符，会把它打印出来 In []: a = '''hello
...: lulu''' In []: a
Out[]: 'hello\nlulu' In []: print a
hello
lulu ---三重引号 -可以是双引号 也可以是单引号 --表解释 这样可以自动把换行符加载 ，不需要自己写
2. 字符串 --是一个序列 -- 对于序列的操作 可以通过索引和切片
In []: b = 'oplkdj' In []: b
Out[]: 'oplkdj' In []: b[]
Out[]: 'o' In []: b[]
Out[]: 'd' In []: b[-]
Out[]: 'j' In []: b[-]
Out[]: 'k' ==========================
/* 取两个字符 */
In []: b[]+b[]
Out[]: 'od' In []: b[:] --从第0个开始取到3个，第三个不显示
Out[]: 'opl'
In []: a = 'abcde' In []: a
Out[]: 'abcde' In []: a[:]
Out[]: 'b' In []: a[:]
Out[]: 'abcde' In []: a[:-]
Out[]: 'abcd'
--0到最后一个，但不取最后一个 In []: a[:]
Out[]: 'ab'
--[:]默认冒号左边为0 In []: a[-]
Out[]: 'e' In []: a[:]
Out[]: 'bcde'
--从1号位取到最后
In []: a[:-]
Out[]: 'abcd' In []: a[::-]
Out[]: 'edcba' In []: a[::]
Out[]: 'abcde' In []: a[::]
Out[]: 'ace' In []: a[::]
Out[]: 'abcde'
In []: a[-:-]
Out[]: 'bc' In []: a[-:-:-]
Out[]: 'dc'
/* 序列*/ In []: a
Out[]: 'abcde' In []: len(a)
Out[]: In []: a + 'f'
Out[]: 'abcdef'
--连接两个序列 //重复序列元素
In []: a *
Out[]: 'abcdeabcdeabcdeabcdeabcde' In []: '' *
Out[]: '' //a为字符串，1为整数，数据类型不符合
In []: a +
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input--a1bd27f4633f> in <module>()
----> a + TypeError: cannot concatenate 'str' and 'int' objects ====================================
//判断某元素是否存在某个变量中
In []: 'a' in a
Out[]: True In []: a
Out[]: 'abcde' In []: 'f' in a
Out[]: False //不存在
In []: 'f' not in a
Out[]: True In []: 'f' not in a+'f'
Out[]: False ====================================
//判断最大最小值
In []: a
Out[]: 'abcde' In []: max(a)
Out[]: 'e' In []: min(a)
Out[]: 'a' ====================================
//比较两个序列是否相等，小于则显示“-1”，大于则显示“1”
In []: cmp(a,'abcde')
Out[]: In []: cmp(a,'abcdef')
Out[]: - In []: cmp(a,'ab')
Out[]: In []: cmp(a,'abcd')
Out[]:
3. 列表
//基本模式
In []: list1 =[] In []: type(list1)
Out[]: list In []: list1
Out[]: [] In []: list2 = ['a',,(,),['hello','python']] In []: list2
Out[]: ['a', , (,), ['hello', 'python']] In []: type(list2)
Out[]: list //元组数量
In []: len(list2)
Out[]: //list的第二个元素
In []: list2[]
Out[]: (,) //替换列表的元素
In []: list2[] = 'b' In []: list2[]
Out[]: 'b' In []: list3 = ['linux'] In []: list2 + list3
Out[]: ['b', , (,), ['hello', 'python'], 'linux'] //往list中新增元素
In []: list3.append('fra') In []: list3
Out[]: ['linux', 'fra']
In []: list1
Out[]: [] //删除某个list
In []: del list1 In []: list1
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
<ipython-input--8304c57391a2> in <module>()
----> list1 NameError: name 'list1' is not defined In []: list2
Out[]: ['b', , (,), ['hello', 'python']] //删除某个元素
In []: del list2[-]
==================================
In []: list2
Out[]: ['b', , (,)] In []: list2
Out[]: ['b', , (,), ] //如果有两个重复的元素，就删除第一个
In []: list2.remove() In []: list2
Out[]: ['b', (,), ]
4. 元组
In []: t = ('a',,(,))
In []: t
Out[]: ('a', , (,))
In []: type(t)
Out[]: tuple //元组
In []: t1 = ()
In []: type(t1)
Out[]: int
In []: t1 = (,)
In []: type(t1)
Out[]: tuple
//加上 逗号，则表示为元组
In []: t = (a, 'b', 'c') In []: t
Out[]: ('abcde', 'b', 'c') // a为变量， 显示时 将变量数值替换 In []: first, second, third = t In []: first
Out[]: 'abcde' In []: second
Out[]: 'b' In []: third
Out[]: 'c'
In []: t.count('b')
Out[]:
In []: t.count('bc')
Out[]:
In []: t.count('abc')
Out[]:
In []: t
Out[]: ('abcde', 'b', 'c')
--- 如果在元组里存在此元素 ，显示“” ，不存在显示“"
//插入列表
In []: list1
Out[]: [] In []: list3
Out[]: ['linux', 'fra']
//(元素的位置， 添加的元组)
In []: list3.insert(, list1) In []: list3
Out[]: ['linux', 'fra', []] In []: list2
Out[]: ['b', (,), ] In []: list2.insert(, list1) In []: list2
Out[]: ['b', [], (,), ]
/* 给列表排序 */
In []: list3.sort() In []: list3
Out[]: [[], 'fra', 'linux']
/* 给列表反转，最后一个变成第一个 */
In []: list2.reverse() In []: list2
Out[]: [, (,), [], 'b'] In []: list2.reverse() In []: list2
Out[]: ['b', [], (,), ]
In []: list1 = [(,),'fra','linux'] In []: list1
Out[]: [(,), 'fra', 'linux'] In []: range()
Out[]: [, , , , ] In []: list1.extend(range()) In []: list1
Out[]: [(,), 'fra', 'linux', , , , , ] In []: list1.extend('abc') In []: list1
Out[]: [(,), 'fra', 'linux', , , , , , 'a', 'b', 'c'] In []: list1.extend(('t1','t2')) In []: list1
Out[]: [(,), 'fra', 'linux', , , , , , 'a', 'b', 'c', 't1', 't2']
5. 字典
In []: info = 'Tom 180 Male' In []: info[:]
Out[]: 'om' In []: info[:]
Out[]: 'Tom' /*
在列表中，取到3，但不会显示3。 在字典中，取到几，就会显示几号位。
*/
In []: list1 = ['name', 'age'] In []: list2 = ['tom', ''] In []: list3 = ['mike',] In []: zip(list1, list2)
Out[]: [('name', 'tom'), ('age', '')] In []: zip(list1, list3)
Out[]: [('name', 'mike'), ('age', )]
In []: dic = {}
In []: type(dic)
Out[]: dict
In []: dic = {'a':, :}
In []: dic
Out[]: {: , 'a': }
In []: dic = {'a':, :, ('a','b'):'hello'}
In []: len(dic)
Out[]:
//获取所有keys
In []: dic.keys()
Out[]: ['a', , ('a', 'b')]
//获取所有values
In []: dic.values()
Out[]: [, , 'hello']
//获取keys的值
In []: dic.get()
Out[]:
In []: dic
Out[]: {: , 'a': , ('a', 'b'): 'hello'}
//修改某个keys的values
In []: dic['a'] =
In []: dic
Out[]: {: , 'a': , ('a', 'b'): 'hello'}
In []: dic[('a', 'b')] = 'linux'
In []: dic
Out[]: {: , 'a': , ('a', 'b'): 'linux'}
//在外部定义一个keys和它的values
In []: dic.get('b', 'python')
Out[]: 'python'
//是否有keys
In []: dic.has_key('a')
Out[]: True
In []: dic.has_key('b')
Out[]: False
//将每一个keys与values都以元组形式展现
In []: dic.items()
Out[]: [('a', ), (, ), (('a', 'b'), 'linux')]
In []: dic
Out[]: {: , 'a': , ('a', 'b'): 'linux'}
//拷贝
In []: dic1 = dic.copy()
In []: dic1
Out[]: {: , 'a': , ('a', 'b'): 'linux'}
In []: dic
Out[]: {: , 'a': , ('a', 'b'): 'linux'}
//更新，则最前面加入新的
In []: dic
Out[]: {: , 'a': , ('a', 'b'): 'linux'} In []: dic1 = {:, :} In []: dic.update(dic1) In []: dic
Out[]: {: , : , : , 'a': , ('a', 'b'): 'linux'} //打包后，将其以字典形式呈现
In []: zip(list1, list2)
Out[]: [('name', 'tom'), ('age', '')] In []: dict(zip(list1, list2))
Out[]: {'age': '', 'name': 'tom'}
/*
以下两种，作用相同，给某个keys赋值*/ In []: dict([('a', ), ('b', )])
Out[]: {'a': , 'b': } In []: dic.fromkeys('ab',)
Out[]: {'a': , 'b': }
