Python notes (i)

String processing
Single and double quotes
. Title (): Capitalize the first letter of each word and the rest of the lower case (regardless of the original)
. Upper (): Capitalize all letters in a string
. Lower (): Change all letters in a string to lowercase
. Strip (): Delete white space (spaces and tabs) at the beginning and end of the line (direct input variable return value to see otherwise no effect)
. Lstrip (): Delete left, which is the beginning of the line
. Rstrip (): Delete the friend side, the end of the
Combine strings directly with a plus sign: +
Escaped (regardless of single double quote):
\ t: Tab
\ n: Line break

字符串反转：    a="abcdef"    a[::-1]：“fedcba”

Variable type conversions
Integer or other---string: str (variable)

Comments
#: Single line comment
"" "" ": Multiline Comment

List
Assignment: var=["AA", "BB" can first create empty list
Return last: Var[-1]
At the end add:. Append ("AAA")
Add at any location:. Insert (index position, "CCC")
Delete: Del var[index position] (the index behind it will replace the deleted index)
. Remove (value): Delete by value, stop only once, and if you delete multiple identical values you need to use loops to determine whether to delete the last element in the clean
Pop-up list:. Pop () (pop-up elements can be used, but not present in the list)
Delete and eject differences: Not available after deletion, pop-up can use this popup element

排序：    .sort()：对列表永久性排序（按照首字母）        反向排序，传递参数：.sort(reverse=True)     sorted(列表)：临时排序，返回排序好的列表，但是对原来的列表无影响        临时反向排序：sorted(列表,reverse=True)倒着打印列表：.reverse()    反转列表：reverse(列表)获取列表长度：len(列表)遍历列表：for i in 列表:    最好的命名方式，列表取复数，遍历变量取单数，即：        for cat in cats:创建数字列表：    range()：生成一串数字         range(1,6)：生成1到5（没有6）         range(2,11,2)：跳着生成    在生成一串数字之后，使用list()将其转换成列表：         list(range(1,6))    上面的可以简写为一行：squares = [value**2 for value in range(1,11)] 找极值：    min(digits)：最小值    max(digits)：最大值    sum(digits)：求和列表切片：    列表[1:4] ：打印从1开始到4的前边3    列表[:4] ：如果不写起始则从头开始    列表[1:] ：如果不写结束则一直到末尾    列表[-5:] ：打印出最后5个元素列表切片可用于遍历一部分列表复制列表：    列表2=列表1[:]（可以指定复制的范围）        后头必须有方括号，否则是两个名字指向同一个列表，不是复制

Tuples: Non-modifiable lists (using the same list)
tuple = (200,50)
print (tuple [0])

不能单独修改一个元素的值，但是可以整体赋值：    

Programming Standards:
Indent to four spaces
Maximum of 80 characters in a row
Empty line don't abuse

If statement
If VAR1=VAR2:
COMMAND
Else
COMMAND

or write:
VAR1 = = VAR2

在判断时区分大小写，如果VAR1位大写，VAR2为小写，则if返回值为FALSE    如果不想区分大小写，可以先使用“.lower()”都转换为小写再比，而且不会影响原来变量中的内容比较符号：    等于：==    不等于：!=    大\小（等）于：>、<、<=、>=    条件与：and（and两边要有空格，和变量分开）（and两边的潘丹条件可使用小括号包裹起来）    条件或：or    判断一个特定的值是否在列表中：in        ‘value‘ in lists        不包含 not in    布尔值：True、False（大小写固定，必须首字母大写）

If format: (Elif and Else sections can be omitted)
If age < 4:
Print ("Your admission cost is $.")
Elif Age < 18:
Print ("Your admission cost is $.")
Else
Print ("Your admission cost is $.")

Working with instances: (judging whether in the list)
requested_toppings = [' mushrooms ', ' extra cheese ']
If ' mushrooms ' in requested_toppings:
Print ("Adding mushrooms.")
If ' pepperoni ' in requested_toppings:
Print ("Adding pepperoni.")
If ' extra cheese ' in requested_toppings:
Print ("Adding extra cheese.")

If lists: (Determines whether the list is empty)

Dictionaries (no order, only concerned with correlation of key-value pairs)
Assignment value:
Alien_0 = {} (create empty dictionary)
Alien_0 = {' Color ': ' green ', ' Points ': 5} (Bulk Assignment)
alien_0[' x_position '] = 0 (discrete assignment)
Use:
Print (alien_0[' color ')) (single printing)
Print (ALIEN_0) (all printed)

Delete: Del alien_0[' points '] traversal dictionary: user_0 = {' username ': ' efermi ', ' first ': ' Enrico ', ' Last ': ' Fermi ',} for key, value in User_0.items (): (using the items function to traverse a key-value pair) (if the items function is not used, and only one variable is output index) for I in Lists.keys (): (traversal index) for I in Lists.values (): (traversal value) (key and value these two words can be arbitrarily UP) The dictionary is unordered, sort it: for name in sorted (Favorite_languages.keys ()): Reject duplicates: For language in Set (Favorite_lang Uages.values ()): Dictionary nesting: Storing a series of dictionaries in a list, or storing a list as a value in a dictionary, which is called nesting. You can nest dictionaries in lists, nest lists in dictionaries, or even nest dictionaries in dictionaries alien_0 = {' Color ': ' green ', ' Points ': 5} alien_1 = {' Color ': ' Yellow ', ' poin TS ': ten} alien_2 = {' Color ': ' Red ', ' Points ':} aliens = [Alien_0, alien_1, alien_2] for alien in a Liens:print (Alien) Output: {' color ': ' green ', ' Points ': 5} {' Color ': ' Yellow ', ' points ': 1 0} {' Color ': ' Red ', ' points ': 15} Dynamically created dictionary saved in list: Aliens =[]    ? For Alien_number in range (30):? New_alien = {' Color ': ' green ', ' points ': 5, ' speed ': ' Slow '}?                                 Aliens.append (New_alien) can then modify the list of contents in the dictionary by traversing the list to save in the dictionary: favorite_languages = { ' Jen ': [' python ', ' Ruby '], ' Sarah ': [' C '], '            Edward ': [' Ruby ', ' Go ', ' Phil ': [' python ', ' Haskell '],} For name, languages in Favorite_languages.items (): Print ("\ n" + name.title () + "s favorite lang         Uages is: ") for language in languages: (Loop included) print (" \ T "+ language.title ()) Dictionary Save Dictionary: (preferably each sub-dictionary contains the same values, so easy to manage) users = {' Aeinstein ': {' first ': ' Albert                             ', ' last ': ' Einstein ', ' Location ': ' Princeton ', }, ' MCUrie ': {' first ': ' Marie ', ' last ': ' Curie ', ' Location ': ' Paris ',},}

Input:
Var_str=input ("Write some Hints Here") (This is Python3, use raw_input in Python2)
Sometimes the hint is that more than one line of information can be stored using a variable (\ n is a newline)
Var_int=int (VAR_STR) (Convert string type to Integer)

while循环：    while 判断条件:（可以是True或False（首字母大写））        continue        break    while和列表搭配：        while lists:（当列表空时结束）            lists.pop()（使用pop函数输出，或者使用remove，不然死循环）                pop：弹出列表中最后一个元素                remove：删除列表中的值，但只删第一个，后头再有重复的不管，当想要删除列表中多个重复的值时，使用while来进行删除                    while ‘cat‘ in pets:                        

Python notes (i)