python基础2之字符串、列表、字典、集合

发布时间：2020-12-16 23:55:22 所属栏目：Python 来源：网络整理

导读：table style="height: 30px; width: 1132px; background-color: #afeeee;" border="0" tr tdspan style="font-size: 16px; font-family: 'Microsoft YaHei';"一、python2 or python3 /td /tr /table 1.PRINT IS A FUNCTION Old: ,2*2 New: ( ,2*2 Old: x, Ol

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<td><span style="font-size: 16px; font-family: 'Microsoft YaHei';">一、python2 or python3</td>
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1.PRINT IS A FUNCTION

Old: ,2*2 New: (,2*2 Old: x, Old: New: () Old: >>sys.stderr, New: (,file= Old: (x,y) New: ((x,y))

2.某些库名改变

3.ALL IS UNICODE NOW

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<td><span style="font-size: 16px; font-family: 'Microsoft YaHei';">二、字符串拼接</td>
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name==+ wd

name= age=22 job= msg=% my name wd age 22 job IT

name= age=22 job= msg= .format(_name=name,_age=age,_job= my name age : 22 job : IT

name= age=22 job= msg= my name age : 22 job : IT

1.字符串常用操作

string string center(self,width,fillchar= string count(self,sub,start=None,end= int decode(self,encoding=None,errors= object encode(self,errors= object endswith(self,suffix,end= bool expandtabs(self,tabsize= string find(self,end= int format(*args,**kwargs): string index(self,end= S.index(sub [,end]]) -> Like S.find() but ValueError when the substring 是否是字母和数字 S.isalnum() -> Return True all characters there at least one character 是否是字母 S.isalpha() -> Return True all characters there at least one character 是否是数字 S.isdigit() -> Return True all characters there at least one character 是否小写 S.islower() -> Return True all cased characters S are lowercase there at least one cased character S.isspace() -> Return True all characters there at least one character S.istitle() -> Return True S a titlecased string there character characters S.isupper() ->

1.列表（list）

列表常用操作：

a=[,,,1,2,3 (a.index()) a=[,,3 (a.index( (a.index(,5)) 3

>>> names = [,,,,, >>> names[1:4] [,, >>> names[1:-1] [,, >>> names[0:3 [,, >>> names[:3] [, >>> names[3:] [,, >>> names[3:-1] [, >>> names[-3:-1] [, >>> names[0::2] [, >>> names[::2] [,]

追加(append)

a=[,3 a.append( [,,,,3,]

a=[, [, a=[, (a) [, a=[, a.pop(2) [,]

a=[,3 a.insert(0,) [,3]

扩展(extend)

a=[, b=[1,3 [,3]

统计(count)

>>> [,,,, >>> >>> [,,, >>> names.reverse() >>> [,]

排序(sort)

>>> [,3 >>> names.sort() File ,line 1, TypeError: unorderable types: int() < str() >>> names[-3] = >>> names[-2] = >>> names[-1] = >>> [, >>> >>> [, >>> names.reverse() >>> [,]

循环(for)

a=[, i d

a=[,, ( oh you are here!

长度（len）

a=[, 3

清空（clear）

a=[, []

列表中含有的方法：

new empty list new list initialized from iterable's items append(self,p_object): count(self,value): integer -- return number of occurrences of value extend(self,iterable): index(self,value,stop=None): integer -- return first index of value. insert(self,index,p_object): pop(self,index=None): item -- remove and return item at index (default last). remove(self,value): reverse(self): sort(self,cmp=None,key=None,reverse=False): -1,1 (self,y): x+y (self,y): y in x (self,y): del x[y] (self,j): del x[i:j] (self,y): x==y (self,name): x.name (self,y): x[y] (self,j): x[i:j] (self,y): x>=y (self,y): x>y (self,y): x+=y (self,y): x*=y (self,seq=()): new empty list new list initialized from iterable's items (self): iter(x) (self): len(x) (self,y): x<=y (self,y): x (self,n): x*n @staticmethod (S,*more): (self,y): x!=y (self): repr(x) (self):

2.元祖（tuple）

索引
切片
循环
长度
包含

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3.字典

字典的特性：

dict是无序的
key必须是唯一的,天生去重

字典操作：

索引(key)

a={:,:,: (a[ WD

增加?

a={:,: a[]= {: ,: ,: ,: }

修改

a={:,: a[]= {: ,: }

删除(del、pop)

>>> {: ,: ,: >>> info.pop() >>> {: ,: >>> info[] >>> {: >>> >>> >>> >>> info = {: ,: >>> {: ,: } >>> (, >>> {: }

查找(get)?

>>> msg={:,:22,: >>> msg[] >>> msg >>> msg.get()

键、值、键值对

msg={:,: (msg.keys()) (msg.values()) (msg.items()) dict_keys([,, dict_values([,22, dict_items([(,),(,22),(,)])

循环（for、enumerate）

key k,v info.items(): enumerate a={:,: i,k enumerate(a.keys()): 0 22 1 2 WD

长度（len）

msg={:,: 3

其他操作（update、setdefault）

update a={:,: b={:,:33,: {: ,: 33,: ,: setdefault a={:,: a.setdefault(, {: ,: 22}

字典中含有的方法：

new empty dictionary new dictionary initialized from a mapping object's new dictionary initialized as if via: new dictionary initialized with the name=value pairs clear(self): None. Remove all items from D. copy(self): a shallow copy of D @staticmethod fromkeys(S,v=None): New dict with keys from S and values equal to v. get(self,k,d=None): D[k] if k in D,else d. d defaults to None. has_key(self,k): True if D has a key k,else False items(self): list of D's (key,value) pairs,as 2-tuples iteritems(self): an iterator over the (key,value) items of D iterkeys(self): an iterator over the keys of D itervalues(self): an iterator over the values of D keys(self): list of D's keys pop(self,d=None): v,remove specified key and return the corresponding value. popitem(self): (k,v),remove and return some (key,value) pair as a setdefault(self,d=None): D.get(k,d),also set D[k]=d if k not in D update(self,E=None,**F): None. Update D from dict/iterable E and F. values(self): list of D's values viewitems(self): a set-like object providing a view on D's items viewkeys(self): a set-like object providing a view on D's keys viewvalues(self): an object providing a view on D's values (self,y): cmp(x,y) (self,k): True if D has a key k,else False (self,y): del x[y] (self,y): x==y (self,name): x.name (self,y): x[y] (self,y): x>=y (self,y): x>y (self,seq=None,**kwargs):

集合是一个无序的，不重复的数据组合，特性：

去重，把一个列表变成集合，就自动去重了
关系测试，测试两组数据之前的交集、差集、并集等关系

常用操作：

s = set([3,5,9,10]) t = set() a = t | s b = t & s c = t – s d = t ^ s t.add() s.update([10,37,42]) t.remove( x x s <= s >= s | s & s - s ^ 返回 set “s”的一个浅复制

1.三级菜单

需求：

1. 运行程序输出第一级菜单2. 选择一级菜单某项，输出二级菜单，同理输出三级菜单3. 菜单数据保存在文件中

代码：

flag= menu_list=[] menu_key=[] menu = {} with open (,,encoding= line msg=line.strip().split() msg[0] menu_key.append(msg[0]) menu_list.append(msg) city menu_key: menu3 = {} each menu_list: city== key,value=each[1].split( )[0],each[1].split( )[1:] menu3[key]=value menu[city]=menu3 i choice=input( choice i1 choice1 = input( choice1 i2 choice2 = input( choice2 == flag = choice2 == ( choice1== flag= choice1== choice== flag=

成都市:高新区 X公司 Y公司 Z公司

menu = exit_flag = current_layer = layers = k choice = input(>: choice == current_layer = layers[-1 choice current_layer: current_layer = current_layer[choice]

（编辑：李大同）

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