>>> menber=["小甲鱼","不定","怡欣","mt"]
>>> for each in menber:
print(each,len(each))
python的内置对象预览:
Number(数字):3.0145,1234,99L,3+4j(负数常量)
String(字符串):'sapm',"红色经'kkk'典"
List(列表):[1,[2,'three points'],4]
Dictionary(字典):{'food':'spam','taste':'yum'}
Tuple(元组):(1,'spam',4,'U')
File(文件):text=open{'segg','r'}.read()
python的比较操作符与java一样
> 大于
< 小于
------------------------------------------------------------
条件分支语法:
①if 条件:
→缩进 条件为真执行
else:
→缩进条件为假执行操作
②while
while 条件:
条件为真执行操作
and逻辑操作运算符
随机:random模块
randint(),会返回一个随机整数
类型转换
整数→字符串str()例如str(132412)变为'132412'
整数→浮点型float()
int()注意:浮点数转换为整数时会采取截断处理。
获取类型信息
type()返回类型
例子:a='reui'
type(a)
isinstance()方法
例子:isistance('eq',str)
返回一个布尔类型值。是否是这个类型
循环:
while 循环:
while 条件:、
循环体
for循环:
for 目标 in 表达式列表:
循环体
range()
语法:range() ([strat,] stop[,step=1])
step=1,默认的值为1;range作用是生产一个从start参数的值开始到stop参数的数字序列
列表:
因为python中变量没有类型,而数组元素的类型是相等的,所以python没有数组,所以列表是加强版的数组~
①创建普通列表
例如:数组名=[1,23,3,4,4,4,4]
②混合列表(列表的成员变量类型包括很多类型)
③创建空列表:empty=[]
对列表的操作:
显示长度→len(列表名)
向列表中添加元素→列表名.append(变量)
向列表中插入列表→列表名.extend([变量1,变量2 ,] )
插入列表中任意位置→列表名.insert(2,"ds") 插入第二个位置
删除列表元素→remove("成员变量")
del menber[4]→删除第五个成员
返回并删除该值→pop(5) 删除第6个元素
列表的分片slice
menber[1:3] :将会显示第二个和第三个成员变量,形成了对源列表的拷贝!
列表的比较操作符:
>>> list1=[123,345]
>>> list2=[234,123]
>>> list1>list2
False
只要列表1的第一个元素大于列表2,那么,后面的数就不用比较了。
+号运算
>>> list1+"xiaojiayu"
Traceback (most recent call last):
File "<pyshell#12>", line 1, in <module>
list1+"xiaojiayu"
TypeError: can only concatenate list (not "str") to list
>>> list1+list2
[123, 345, 234, 123]
>>>
*号运算
>>> list1*3
[123, 345, 123, 345, 123, 345]
>>> list5=[123,["xiaojiayu","why"]]
>>> list4=[123,"xiaojiayu","why"]
>>> "why" in list4
True
>>> "why" in list5
False
>>>
查看list的内置函数:
>>> dir(list)
['__add__', '__class__', '__contains__', '__delattr__', '__delitem__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', '__iter__', '__le__', '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', 'append', 'clear', 'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']
>>>
使用:
count 计数
>>> list4.count(123)
1
转置reverse()
排序sort(0):默认是从小到大排序
>>> list6=[1,0,9,5,4,7,6,2,11,10]
>>> list6.sort()
>>> list6
[0, 1, 2, 4, 5, 6, 7, 9, 10, 11]
>>> list6.reverse()
>>> list6
[11, 10, 9, 7, 6, 5, 4, 2, 1, 0]
>>>
或者
>>> list6.sort(reverse=True)
>>> list6
[11, 10, 9, 7, 6, 5, 4, 2, 1, 0]
>>>
列表的复制:
>>> list7=list6[2:9]
>>> list7
[9, 7, 6, 5, 4, 2, 1]
如果是用=号时,就是给这个列表起了另一个名字,而分片儿复制则会在内存中实实在在的分配存储空间。
元组:戴上了加锁的列表(不能随意插入,删除等操作)
>>> tuple1=(1,2,3,5,8,6,9)
>>> tuple1
(1, 2, 3, 5, 8, 6, 9)
>>> tuple1[3]
5
>>> tuple1[1:3]
(2, 3)
>>> temp=(1)
>>> type(temp)
<class 'int'>
>>> type(temp1=(1,))
TypeError: type() takes 1 or 3 arguments
>>> temp=(1,)
>>> type(temp)
<class 'tuple'>
>>>
插入操作:(生成新的元组)
>>> temp=("意境","和","下架与")
>>> temp=temp[:2]+("哇")+temp[2:]
Traceback (most recent call last):
File "<pyshell#50>", line 1, in <module>
temp=temp[:2]+("哇")+temp[2:]
TypeError: can only concatenate tuple (not "str") to tuple
>>> temp=temp[:2]+("哇",)+temp[2:]
>>> temp
('意境', '和', '哇', '下架与')
>>>
字符串之内置方法
>>> str='i am fool ,yami'
>>> str
'i am fool ,yami'
>>> find("fool")
Traceback (most recent call last):
File "<pyshell#19>", line 1, in <module>
find("fool")
NameError: name 'find' is not defined
>>> find('fool')
Traceback (most recent call last):
File "<pyshell#20>", line 1, in <module>
find('fool')
NameError: name 'find' is not defined
>>> str.find('fool')
5
>>> str.join('123')
'1i am fool ,yami2i am fool ,yami3'
>>> "{a} love {b} {c}".format("i" ,"want" ,"to do")
Traceback (most recent call last):
File "<pyshell#23>", line 1, in <module>
"{a} love {b} {c}".format("i" ,"want" ,"to do")
KeyError: 'a'
>>> "{a} love {b} {c}".format(a="i" ,b="want" ,c="to do")
'i love want to do'
>>> "{1} love {2} {3}".format("i" ,"want" ,"to do")
Traceback (most recent call last):
File "<pyshell#25>", line 1, in <module>
"{1} love {2} {3}".format("i" ,"want" ,"to do")
IndexError: tuple index out of range
>>> "{0} love {1} {2}".format("i" ,"want" ,"to do")
'i love want to do'
>>>
序列:
列表,数组和字符串的共同点
可以通过索引得到每个元素
索引默认为从0开始
可以通过分片的方法得到一个范围内的元素的集合
共同操作符
list()将一个可迭代对象转换为列表
list(iterable) -> new list initialized from iterable's items
>> help(list)
Help on class list in module builtins:
class list(object)
| list() -> new empty list
| list(iterable) -> new list initialized from iterable's items
|
| Methods defined here:
|
| __add__(self, value, /)
| Return self+value.
|
| __contains__(self, key, /)
| Return key in self.
|
| __delitem__(self, key, /)
| Delete self[key].
|
| __eq__(self, value, /)
| Return self==value.
|
| __ge__(self, value, /)
| Return self>=value.
|
| __getattribute__(self, name, /)
| Return getattr(self, name).
|
| __getitem__(...)
| x.__getitem__(y) <==> x[y]
|
| __gt__(self, value, /)
| Return self>value.
|
| __iadd__(self, value, /)
| Implement self+=value.
|
| __imul__(self, value, /)
| Implement self*=value.
|
| __init__(self, /, *args, **kwargs)
| Initialize self. See help(type(self)) for accurate signature.
|
| __iter__(self, /)
| Implement iter(self).
|
| __le__(self, value, /)
| Return self<=value.
|
| __len__(self, /)
| Return len(self).
|
| __lt__(self, value, /)
| Return self<value.
|
| __mul__(self, value, /)
| Return self*value.n
|
| __ne__(self, value, /)
| Return self!=value.
|
| __new__(*args, **kwargs) from builtins.type
| Create and return a new object. See help(type) for accurate signature.
|
| __repr__(self, /)
| Return repr(self).
|
| __reversed__(...)
| L.__reversed__() -- return a reverse iterator over the list
|
| __rmul__(self, value, /)
| Return self*value.
|
| __setitem__(self, key, value, /)
| Set self[key] to value.
|
| __sizeof__(...)
| L.__sizeof__() -- size of L in memory, in bytes
|
| append(...)
| L.append(object) -> None -- append object to end
|
| clear(...)
| L.clear() -> None -- remove all items from L
|
| copy(...)
| L.copy() -> list -- a shallow copy of L
|
| count(...)
| L.count(value) -> integer -- return number of occurrences of value
|
| extend(...)
| L.extend(iterable) -> None -- extend list by appending elements from the iterable
|
| index(...)
| L.index(value, [start, [stop]]) -> integer -- return first index of value.
| Raises ValueError if the value is not present.
|
| insert(...)
| L.insert(index, object) -- insert object before index
|
| pop(...)
| L.pop([index]) -> item -- remove and return item at index (default last).
| Raises IndexError if list is empty or index is out of range.
|
| remove(...)
| L.remove(value) -> None -- remove first occurrence of value.
| Raises ValueError if the value is not present.
|
| reverse(...)
| L.reverse() -- reverse *IN PLACE*
|
| sort(...)
| L.sort(key=None, reverse=False) -> None -- stable sort *IN PLACE*
|
| ----------------------------------------------------------------------
| Data and other attributes defined here:
|
| __hash__ = None