Python list, dictionary, string Common operations

1. String manipulation

The string can be evaluated by subscript, but because the string is an immutable variable, the value cannot be modified by subscript.

str = ' Lily Terry Mark '

Name[0] #获取第1个字符串值

Name[0:7] #获取第1 The string value of the ~

Name[:7] #缺省开始位置, the default value starts from the 1th element

Name[0:] #缺省结束位置, default to end of String end

The string contains the judgment operator: in, not in, is

' Lily ' in Names

' Lily ' not in Names

' Lily ' is ' lily ' is judging if the same memory address

A For loop inside python that loops through every element of an object

For name in Names:
Print (' name: ', name)

String Other operations

s = ' Hello World '

S.capitalize () # Capitalize first letter

S.center (50, ' _ ')) # Total length 50, put s in the middle

S.endswith (' u ') # does it end with X

S.expandtabs (30) # Number of times to fill \ t

S.find (' World ', 0,15) # Find the index of the string, find the index that returns the first occurrence, cannot find the return-1

S.rfind (' wo ') # reverse lookup, returns the subscript of the rightmost character

Formatting of strings

S.format (s= ' Lily ', age=18)) # format characters

S.format_map ({' s ': ' Lily ', ' age ': 19})

string format judgment
' AbA123 '. Isalnum () # contains numbers and letters

' AbA '. Isalpha () # is the English alphabet

' 122 '. IsDigit () # is a number

' AA '. Isidentifier () # is a valid variable name

' AA '. Islower () # Whether it is a lowercase letter

String case

' AA '. Isupper () # is an uppercase letter
S.lower () # Turns lowercase
S.upper () # becomes uppercase

' Abcde '. Swapcase () # case reversal

String to go to space

' \nmysql \ n '. Lstrip () # By default, the left space and line breaks are removed
' \nmysql \ n '. Rstrip () # Recognize and remove the right space and line breaks
' \nmysql \ n '. Strip () # Default to remove both spaces and line breaks
' MySQL '. Strip (' m ') # When a string is passed in, only the specified string is removed

String mappings

p = Str.maketrans (' abcde ', ' 12345 ') #前面的字符串和后面的字符串映射
Print (' Ccab '. Translate (p)) #输出按照上面maketrans做映射后的字符串

String substitution

' MySQL is db. MySQL '. replace (' MySQL ', ' Oracle ') #替换字符串

String cutting

' 1+2+3+4 '. Split (' + ') # cuts A string, returns a list, separates the string by the specified string, and then places it in a list
# If you don't write anything, separated by a space, multiple spaces are counted as a
' 1+2\n1+2 '. Splitlines () # Split by line break

String connection

Print (' + '. Join ([' hhe ', ' haha ', ' ee ')) # The Join method is used to stitch up each element of an iterative object through a string

String combinations

Import string
Print (string.ascii_letters+string.digits) # Case Letter + number
Print (string.ascii_lowercase) # lowercase Letter
Print (string.ascii_uppercase) # Uppercase
Print (string.digits) # all numbers
Print (string.hexdigits) #所有数字 + uppercase and lowercase letters

Built-in functions for working with strings

Len (str) #串长度

CMP ("Myfriend", str) #字符串比较. First large, returns 1

Max (' abcxyz ') #寻找字符串中最大的字符

Min (' abcxyz ') #寻找字符串中最小的字符

String conversions

Float (str) #变成浮点数, float ("1e-1") results are 0.1

int (str) #变成整型, int ("12") result is 12

Int (str,base) #变成base进制整型数, int ("11", 2) result is 2

Long (str) #变成长整型,

Long (str,base) #变成base进制长整型,

2. List operation

Create a list

Names =[1,2,3, "Lily", "Mark" # Definition List

List operations

Print (names[3]) # The 4th list element value is taken by subscript

Print (names[-1]) # subscript is-1, which means the last element is taken.

Names[0]= ' Terry ' # modifies the first list element value

List element Additions

L.append (VAX) # Adds a value to the list from the end
L.insert (Index,vax) #在指定的索引处添加元素

List element deletion

L.pop (index) #缺省index返回最后一个元素 and removed from list without deleting the element at the specified position by default

L.remove (Var) #删除指定的值, and pop method to distinguish, pop if deleted, the pass is subscript, remove is a value of an element

DELL[1] #删除指定下标的元素

Dell[1:3] #删除指定下标范围的元素

List Element Lookup

L.index (var,start,stop) #返回该元素的索引, start to stop specifies the range, returns the first if there is more than one, returns an exception

L.count (Var) #该元素在列表中出现的个数, not found for 0

List sort

L.sort () #排序

L.reverse () #倒序

List element Merging

L1+L2 #列表操作符 "+", two lists merged

L.extend (list) #把另一个列表每个值逐一添加到前面的列表中 list empty l.clear ()

Loop List

For name in Names:
Print (name)

Multidimensional arrays
List = [1,2,3,4,5, ' Lily ', 23.3,[' mark ', ' Lucy ', [' name ', ' sex ']]

3. Dictionary operation

Create a dictionary

DiC = {' stu1 ': ' Mark ', ' stu2 ': ' Lucy ', ' stu3 ': ' Lilei '}

Dictionary additions or modifications

Dic[key] = value

Dictionary Delete

Dic.pop (key) # standard method of deletion
del Dic[key] # using the Del method to delete
Dic.popitem () # randomly deletes a value

Dictionary Lookup

Dic.get (Key) # Gets the value of key for, which returns none if key does not exist
Dic[' Marry ' # gets the value of key for this method if key does not exist, it will be an error
' Marry ' in dic # Determines whether marry is in the dictionary, returns TRUE or False

Dictionary built-in methods
Dic.values () #以列表的形式返回字典中的值, the list of return values can contain repeating elements
Dic.keys () #返回字典键的列表
Dic.setdefault (Key, Value) # If this key exists, then do not move it, do not exist, add a
Dic.update (DIC2) # Updates the dictionary value, if key exists, it is updated, does not exist to add
Dic.items () # Dictionary converted to a list

Dictionary loops
DiC = {' stu1 ': ' Mark ', ' stu2 ': ' Lucy ', ' stu3 ': ' Lilei '}
For K in DiC:
Print (K,dic[k]) #打印key和value的值, recommended this way, faster

4, tuple operation

A python tuple is similar to a list, except that the elements of a tuple cannot be modified.

Tuple= (' A ', ' B ', ' C ', ' d ', ' e ')

tuple = (' a ',) #元组中只包含一个元素时, you need to add a comma after the element

accessing tuples

Tuple[key]

modifying tuples

element values in tuples are not allowed to be modified, but they can be combined in groups of tuples

Tuple1+tuple2

Delete a tuple

element values in tuples are not allowed to be deleted, but you can use the DEL statement to delete an entire tuple

Del tuple

Tuple built-in functions

CMP (TUPLE1,TUPLE2) # Comparison of two elements

Len (tuple) #计算元组元素个数

Max (tuple) #返回元组中最大值

Min (tuple) #返回元组中最小值

Tuple (seq) #将列表转换为元组

Python list, dictionary, string Common operations