Python Learning Note 2: List, dictionary, string manipulation

A module

A module is a code that someone else has written and can be referenced by an import. A standard library is a library that is officially released by Python and is installed by default when you install Python.

1.os

and system-related, such as:

>>> Os.system ("LS-LRTHF")
Total 20M
-rw-r--r--. 1 root root 20M Jul 13:48 python-3.5.2.tgz
-RW-------. 1 root root 958 Jul 19:34 anaconda-ks.cfg
Drwxrwxr-x. 4.0K Jul 23:36 python-3.5.2/

>>> os.path.isfile ("/root")
False
>>> Os.path.isdir ("/root")
True

Two lists

name = ["NAME0", "name1", "name2"]

1. Index Operations:

>>> Name[0]
' NAME0 '
>>> Name[1]
' Name1 '

The list is sequential.

2. Shard Operation:

>>> Name[0:2]
[' NAME0 ', ' name1 ']
>>> Name[-1]
' Name2 '
>>>

When you don't know the length of the list, 1 is a good choice.

3. Append operation:

>>> name.append ("Name3")
>>> Name
[' NAME0 ', ' name1 ', ' name2 ', ' Name3 ']
>>>

4. Delete the element:

>>> name.remove ("name2")
>>> Name
[' NAME0 ', ' name1 ', ' Name3 ']
>>> Name.pop ()
' Name3 '
>>> Name
[' NAME0 ', ' name1 ']
>>>

The Remove method deletes the specified element, the Pop method deletes the last element, and returns the element value

5. Modify the element:

>>> Name
[' NAME0 ', ' name1 ', ' name2 ']
>>> name[2]= "Name6"
>>> Name
[' NAME0 ', ' name1 ', ' Name6 ']
>>>

6. Membership: In

>>> name = ["NAME0", "name1", "name2"]
>>> "Name1" in Name
True
>>> "Name5" in Name
False
>>>

Three dictionaries

Dictionaries are key-value pairs, and k-v pairs are unordered, so there is no index operation, by using key to access value values, the key value is equivalent to the index, cannot be duplicated

>>> dic={"name": "Shirley", "Age": "+", "job": "Teacher", "country": "China"}
>>> DIC
{' Country ': ' China ', ' name ': ' Shirley ', ' age ': ' + ', ' job ': ' Teacher '}

1. Increase

>>> DIC
{' Country ': ' China ', ' name ': ' Shirley ', ' age ': ' + ', ' job ': ' Teacher '}
>>> dic["School"]= "Qinghua"
>>> DIC
{' Country ': ' China ', ' name ': ' Shirley ', ' age ': ' + ', ' job ': ' Teacher ', ' school ': ' Qinghua '}
>>>

2. Modifications

>>> dic["School"]= "Beida"
>>> DIC
{' Country ': ' China ', ' name ': ' Shirley ', ' age ': ' + ', ' job ': ' Teacher ', ' school ': ' Beida '}
>>>

3. Delete

>>> Dic.pop ("Age")
' 26 '
>>> DIC
{' Country ': ' China ', ' name ': ' Shirley ', ' job ': ' Teacher ', ' school ': ' Beida '}
>>>

>>> del dic["job"]
>>> DIC
{' Country ': ' China ', ' name ': ' Shirley ', ' School ': ' Beida '}
>>>

Del is a universal function

4. Get the value

>>> DIC
{' Country ': ' China ', ' name ': ' Shirley ', ' age ': ' + ', ' job ': ' Teacher ', ' school ': ' Qinghua '}
>>> dic.get ("name")
' Shirley '
>>> dic["Name"]
' Shirley '
>>> dic.get ("lll")
>>> DiC. ["LLL"]
File "<stdin>", line 1
Dic. ["LLL"]
^
Syntaxerror:invalid syntax
>>>

Get returns None when no key is used, and an error occurs when using the index operation.

6. Memberships

>>> "Name" in DIC
True
>>>

7. Cyclic DIC

info={' 1 ': "100", "2": "200", "3": "300", "4": "400", "5": "500"}
For key in info:
   Print (Key,info[key])

5 500
4 400
3 300
1 100
2 200

8. Keys () method

>>> Dic.keys ()
Dict_keys ([' Country ', ' name ', ' age ', ' job ', ' school ')

Returns a key as a list

Four-string method

A.format_map () #传入的参数是字典

A.index () #同find () method

A.isalnum () #检测字符串是否由字母和数字组成

A.isalpha () #检测字符串是否只由字母组成

A.isdigit () #判断字符串是不是数字

A.isidentifier () #判断字符串是否是合法的标识符

A.islower () #判断是不是小写

A.isnumeric () #检测字符串是否只由数字组成

A.isspace () #判断字符串是否仅包含空格或制表符. Note: space characters are different from whitespace

A.istitle () #判断字符串是不是标题格式

A.isupper () #判断是不是大写

A.join () #连接字符串数组. Generates a new string from a string, tuple, or element in the list, with the specified character (delimiter) connection

A.ljust () #返回一个原字符串左对齐 and fills a new string of the specified length with a space.

A.lower () #把大写转成小写

A.lstrip () #去掉字符串左边的空格

A.maketrans () #将左右参数对应, replace the left argument with the right argument

A.replace () #把字符串中的 old (older string) replaced with new

A.rfind () #返回字符串最后一次出现的位置, returns 1 if no match is found

A.rindex () #返回子字符串 the last occurrence of str in a string

A.rjust () #返回一个原字符串右对齐 and fills a new string with a space to a specified length

A.rsplit () #去掉右边空格或换行符

A.rstrip () #去掉字符串右边的空格

A.strip () #去掉字符串中的空格

A.split () #字符串切片

The A.splitlines () #按行分隔 Returns a list that contains rows as elements, and if NUM specifies that only num rows are sliced.

A.startswith () #判断是不是以参数中内容开头

A.swapcase () #对字符串的大小写字母进行转换

A.title () #把字符串转成标题格式

A.capitalize () #把字符串首字母变为大写

A.endswith () #判断字符串是否以指定字符或子字符串结尾, commonly used to determine file types

A.expandtabs () #把字符串中的 the tab sign (' \ t ') to a space, returning the new string generated after the tab symbol (' \ t ') in the string is converted to a space

A.format () #格式化字符串

A.find () #返回参数在字符串中首次出现的位置

Python Learning Note 2: List, dictionary, string manipulation