Python data operations, dictionaries, lists

Source: Internet
Author: User
Tags constant definition

Constant definition rule: constant meaning is not changed; Constant definition name is all uppercase;

such as: mysql_connection= ' 192.168.1.1 '

Pyc:python generated translation files that enable the computer to recognize the Python language;

Syntax and use of the list:

List parameter insertion syntax: Name.insert (2, ' Minggou ')

NAME[1] = "Wangminglong"---> Modify the contents of the corresponding field in the list;

Append: Name.append ("Alex")

Delete: Name.remove ("Minggou")

Definition list: name=["1", "Minghu", 2,43, "Minggou"]

Step: Print (Name[::2]) every other place value once;

Query list: which in name

If 9 in Name:

Num_of_ele = Name.count (9)

Position_of_ele = Name.index (9)

Name[position_of_ele] = 999

Print ("[%s] 9 is in name,postion:[%s]"% (Num_of_ele,position_of_ele))

Print (name)

For I in Range (Name.count (9)): #修改所有9

Ele_index = Name.index (9)

Name[ele_index] = 9999999

Print (name)

List Merge:

Name.extend (name2)

List inversion:

Name.reverse ()

List sort:

Name.sort () #字符串和数字结合排序, Python3 will be an error, separate row will not error

Enter the subscript to delete the element and delete the last one by default:

Name.pop ()

Copy the list, copy only the first layer, do not copy the second layer, the second layer copies the memory data sharing:

Name.copy ()

List nesting:

name = ["CSD", "Asvs", [2,3,56,7], "CDC", 354]

View List Length:

Print ("Name", Len (name))

Read-only list:

R = (1,2,3,4,5) #不想被改动的列表, read-only list, tuple;

String Common operations:

name = "Qiu Ye"

Username = input ("Name:")

If Username.strip () = = ' Qiuye ': #移除空格;

Print ("Welcome")

String segmentation:

names = "Dwqd,ascd,frer"

name2 = Names.split (",")

Print (name2) #变为列表

Print ("|". Join (name2)) #按 | to split the output;

String index:

name = "Qiu Ye"

Print ("in name) #判断字符串中是否有空格

Print (Name.capitalize ()) #首个字母大写

Name.format () #字符串格式化

Cases:

msg = "Hello,{name},it ' The {age} last time ..."

MSG2 = Msg.format (name= ' Minghu ', age=333)

Print (MSG2)

MSG2 = "Hh{0},ddas{1}"

Print (Msg2.format ("Alex", 33))


Slices: Slice with same list

name = "Alex Li"

Print (Name[2:4])

Print (Name.center, '-') #40个字符居中打印, other bytes used-instead;

Print (Name.find ()) #指定字段查找并输出;

Judge:

age = Int (input ("Your Age:"))

If Age.isdigit (): #判断是否为数字

age = Int (age)

Else

Print ("Invalid data type")

Name.isalnum () #不能包含特殊字符

Name.endswith () #判断结束

Name.startswith () #判断开始

Name.upper () #大写

Name.lower () #小写

Data operations:

Type ("333") is Str

Type (a) is List

Binary representation:

256 128 64 32 16 8 4 2 1

0 0 0 0 0 0 0 0 0

1 1 1 1 1 1 1 1 1

The smallest unit that can be represented in a computer is a bits;

The smallest unit that can be stored in a computer is a bits (bit)

8bit = byte (bytes)

1024byte = 1 KByte

1204kbyte = 1mbyte

1024MB =1GB

Operator:

<< Right Shift

>> left Shift

Cases:

64>>2 = = 16

64<<1 = = 128

Python dead Loop:

Cases:

Count = 0

While True:

Print ("This is true", count)

Count +=1

Dictionary:

id_db ={

1248357148965: {#key值必须是唯一的, otherwise only the last one is output;

' Name ': ' Shanpao ', #name: Dictionary key, ' Shanpao ': Key's value

' Age ': ' 24 '

' Addr ': ' Dongbei '

},

1248357448965: {

' Name ': "Shanpao",

' Age ': ' 24 '

' Addr ': ' Dongbei '

},

124835712345: {

' Name ': "Shanpao",

' Age ': ' 24 '

' Addr ': ' Dongbei '

},

}

#字典的基本格式, the storage information is more flexible;

Assign a new value to key:

id_db[1248357448965][' name '] = "new value" #修改value;

id_db[1248357448965][' qq_of_wife ' = 123556675 #如果字典中没有此value, the new value is added;

Print (Id_db.setdefault (234254364), "HHH")) #取一个默认值, if not present, assigns a new value;

Print (Dict.fromkeys ([1,2,34,5,6,8], ' DDD ')) #将列表中每个值拿出来当做场景使用---> A pit!

Id_db.popitem () #随机删除字典中的一个key---> recommends not to use any random language;

High-efficiency loops:

For key in id_db:

Print (Key,id_db[key])




Example: Shopping Cart

salary =  () Salary.isdigit ():    salary =  (Salary):      () Welcome_msg = .center (,) (welcome_msg) exit_flag =product_list = [      (,),     (,),     (,),     (,),      (,),     (,),     (,),]shop_car = []    exit_flag :     (. Center (,))     item  (product_ List):        index = item[]         p_name = item[][]        p_price =  item[][]         (Index,,p_name,p_price)      user_choice =  ()     user_choice.isdigit (): user_choice =  (user_ Choice)         user_choice <  (product_list):             p_item = product_list[user_choice]             p_item[] <= salary:  shop_car.append (P_item)    salary -= p_item[]  (% (p_item,salary))              :                  (% salary)     :        user_ choice == user_choice == :              (. Center (,))             item shop _car:                 (item)              (. Center (,))               (% salary)             exit_ flag = user_choice == user_choice == :              (. Center (,))              item shop_car:                  (item)              (. Center (,))               (% salary)


Python data operations, dictionaries, lists

Related Article

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.