Python Basics-The next day

The content of this article:

1. Lists (list)

2. Tuples (tuple)

3. Dictionary (dict)

4. Manipulation of strings

One, List

1. Defining the list

List_name = ["Element 1", "Element 2"]

A pair of brackets [] is the definition list;

if the element is a string, enclose it in double or single quotation marks;

2. Take the elements in the list

Show all the contents of a list

>>> city = ["Beijing", "Shanghai", "Guangzhou", "Nanjing"]>>> Print (city) [' Beijing ', ' Shanghai ', ' Guangzhou ', ' Nanjing ']

Take a single element in a list

>>> city = ["Beijing", "Shanghai", "Guangzhou", "Nanjing"]>>> print (city[0]) beijing>>> Print (city[3]) nanjing>>> print (city[-1]) Nanjing #-1 represents the last element of the list

Above is the subscript from the list of elements, the subscript starts from zero.

Add a small content, and take the element through a For loop:

>>> city = ["Beijing", "Shanghai", "Guangzhou", "Nanjing"]>>>-Place_name in City:print _NAME)-----The following is what is displayed-----beijingshanghaiguangzhounanjing

3. Slicing

>>> city = ["Beijing",  "Shanghai",  "Guangzhou",  "Nanjing"]>>>  print (City[0:2]) [' Beijing ',  ' Shanghai ']  #  shows all elements from subscript 0 to 2, but does not include the contents of subscript 2. >>> print (city[-3:-1]) [' Shanghai ',  ' Guangzhou ']  #  note that the order from the list is removed from left to right. >>> print (City[:2]) [' Beijing ',  ' Shanghai ']  #  if the start subscript is 0, you can omit to write. >>> print (city[1:]) [' Shanghai ',  ' Guangzhou ']  #  If the end subscript is-1, you can also omit to write. >>> print (city[:]) [' Beijing ',  ' Shanghai ',  ' Guangzhou ',  ' Nanjing ']#  When the start subscript and end subscript are omitted, it represents all the elements in the list >>>city = ["Beijing",  "Shanghai",  "Guangzhou",  " Nanjing ", " Wuhan "]>>> print (City[0:-1:2])   #[start subscript, end subscript, step [' Beijing ',  ' Guangzhou ']   #注意, the last Wuhan not shown, is Gu Tou regardless of the tail of the >>> print (City[::2]) [' Beijing ',  ' Guangzhou ',   ' Wuhan ']   #省略了开头和结尾, Wuhan is displayed.

4. Adding elements

Append:

>>> city = ["Beijing", "Shanghai", "Guangzhou", "Nanjing"]>>> city.append ("Wuhan") >>> print (city) [' Beijing ', ' Shanghai ', ' Guangzhou ', ' Nanjing ', ' Wuhan ']# add content in a way that is appended, so the new additions are in the last side of the list

Insert:

>>> city = ["Beijing", "Shanghai", "Guangzhou", "Nanjing"]>>> City.insert (1, "Wuhan") >>> Print (city) [' Beijing ', ' Wuhan ', ' Shanghai ', ' Guangzhou ', ' Nanjing ']# inserts the new content at the specified subscript

5. Change the contents of the list

>>> city = ["Beijing", "Shanghai", "Guangzhou", "Nanjing"]>>> city[3] = "Wuhan" >>> print (city ) [' Beijing ', ' Shanghai ', ' Guangzhou ', ' Wuhan ']

6. Delete the contents of the list

Delete Using Del

>>> city = ["Beijing", "Shanghai", "Guangzhou", "Nanjing"]>>> del city[0]>>> print (city) [' Wuhan ', ' Shanghai ', ' Guangzhou ', ' Nanjing ']>>> del City #删除整个列表

Remove with Remove

>>> city = ["Beijing", "Shanghai", "Guangzhou", "Nanjing"]>>> City.remove ("Shanghai") >>> Print (city) [' Beijing ', ' Wuhan ', ' Guangzhou ', ' Nanjing ']

7. Find the elements in the list

Use index to find unique elements

>>> city = ["Beijing", "Shanghai", "Guangzhou", "Nanjing"]>>> Print (City.index ("Shanghai")) 1 # The index of the element is displayed

Use Count to find the number of identical elements

>>> city = ["Beijing", "Shanghai", "Guangzhou", "Beijing"]>>> Print (City.count ("Beijing")) 2 # It shows how many Beijing this element is in total.

8. Empty the elements in the list

>>> city = ["Beijing", "Shanghai", "Guangzhou", "Nanjing"]>>> city.clear () >>> Print []

9. Merging lists

>>> city1 = ["Beijing", "Shanghai"]>>> city2 = ["Guangzhou", "Nanjing"]>>> City1.extend ( City2) >>> print (city1, city2) [' Beijing ', ' Shanghai ', ' Guangzhou ', ' Nanjing ' [' Guangzhou ', ' Nanjing '] # Note that City2 list is still here!

Two, tuple (tuple)

1. What is a tuple

tuples are in fact the same as the list, but also save a group of numbers, but once it is created, it can no longer be modified, can only slice and query, which means it only has 2 methods, one is Count , one is index.

2. Definition of a tuple

Tuple_name = ("element 1", "Element 2")

3. Taking elements from a tuple

>>> City = ("Beijing", "Shanghai", "Guangzhou", "Nanjing") >>> print (' Beijing ', ' Shanghai ', ' Guangzhou ', ' Nanjing ') >>> print (city[0]) beijing>>> print (City[0:2]) (' Beijing ', ' Shanghai ') # Shards and lists are the same!

4. Finding elements in tuples

>>> City = ("Beijing", "Shanghai", "Guangzhou", "Nanjing") >>> Print (City.index ("Shanghai")) 1 # The index of the element is displayed >>> city = ("Beijing", "Shanghai", "Guangzhou", "Beijing") >>> print (City.count ("Beijing") ) 2 # shows the number of Beijing this element in total

Three, dictionary (dict)

1. Introduction Dictionary

Dictionary a Key-value data type, using the same dictionary as we used to go to school, check the details of the corresponding page by strokes and letters.

2. Definition of a dictionary

>>> dict_name = {"Key1": "Value1", "Key2": "Value2",>>>}

the key in the dictionary is unique, which also means that the dictionary is inherently de-re-functional;

The dictionary does not have subscript, look up dictionary content is through key to find;

Dictionaries are unordered, and each time the dictionary content is displayed, the order of the contents is different;

3. Find content in a dictionary

>>> City = {"Beijing": "Haidianqu", "Shanghai": "Pudongxinqu", "Guangdong": "Guangzhou", ;>>}>>> Print (city["Beijing"]) haidianqu>>> print (City.get ("Beijing")) haidianqu>> > Print (City.get ("Hubei")) None # when unsure if the key exists, you can use this method if you don't have the key and return none without an error >>>

4. Modify and Add content

>>> City = {"Beijing": "Haidianqu", "Shanghai": "Pudongxinqu", "Guangdong": "Guangzhou", ;>>}>>> city["Beijing"] = "Chaoyangqu" # when the key is modified >>> print (city) {' Shanghai ': ' Pudongxinqu ', ' Guangdong ': ' Guangzhou ', ' Beijing ': ' Chaoyangqu '}>>> city[' hubei ' = ' Wuhan ' # Add content >>> PR when there is no key Int (city) {' Shanghai ': ' Pudongxinqu ', ' Beijing ': ' Chaoyangqu ', ' Hubei ': ' Wuhan ', ' Guangdong ': ' Guangzhou '}

5. Delete

>>> City = {"Beijing": "Haidianqu", "Shanghai": "Pudongxinqu", "Guangdong": "Guangzhou", ;>>}>>> del city["Beijing"] # Delete the specified key >>> print (city) {' Guangdong ': ' Guangzhou ', ' Shanghai ': ' Pudongxinqu '}>>> city.pop ("Shanghai") # Delete the specified key >>> print (city) {' Guangdong ': ' Guangzhou '}

6. Determine if key exists

>>> City = {"Beijing": "Haidianqu", "Shanghai": "Pudongxinqu", "Guangdong": "Guangzhou", ;>>}>>> Print ("Beijing" in the city) # Specifies that the key exists when it returns True, and returns false when it does not exist. True

7. Merging dictionaries

>>> city1 = {"Beijing": "Haidianqu", "Shanghai": "Pudongxinqu",>>>}>>> city2 = {"Beijing": "Chaoyangqu", "Guangdong": "Guangzhou",>>>}>>> city1.update (city2) >>&G T Print (city1) {' Shanghai ': ' Pudongxinqu ', ' Beijing ': ' Chaoyangqu ', ' Guangdong ': ' Guangzhou '}# two dictionaries have the same key, but value is different, The combined value is a different key in the value# two dictionary in City2, which is directly the contents of the merged dictionary.

8. Using in the For loop

>>> City = {"Beijing": "Haidianqu", "Shanghai": "Pudongxinqu", "Guangdong": "Guangzhou", ;>>}>>> for Place_name in city:>>> print (place_name) Guangdongbeijingshanghai # Show only key Oh >&G T;> for Place_name in city:>>> print (Place_name, city[place_name]) Guangdong guangzhoubeijing Haidianqushan Ghai Pudongxinqu # This is how key and value are displayed.

Iv. manipulation of strings

>>> Print ("Checklist". Center (10, "+")) ++++ List ++++ # only 10 strings are displayed, specifying the contents if there are No 10 strings, use + to complement each other at both ends

>>> print ("--\t--". Expandtabs (tabsize=5))----# tab equals 5 spaces

>>> print ("Abcdefghijk". Find ("D")) 3 # Here is the subscript, oh, is not an instant thought of the string can also do slices. >>> print ("Abcdefghijk" ["Abcdefghijk". Find ("D"): 7]) DEFG # is still Gu Tou regardless of the tail

>>> print ("Abc{d}e{f}". Format (d= "Y", f= "Z") Abcyez # content substitution

>>> Print ("1". IsDigit ()) true>>> print ("a". IsDigit ()) False # judgment is not an integer

>>> print ("AbcD". Isalpha ()) true>>> print ("Abcd1". Isalpha ()) False # Determines if there are only letters in the content

>>> print ("ABCDEFG". Islower ()) True # determines whether the content is not only lowercase letters >>> print ("ABCD". Isupper ()) True # Judge whether the English in the content is uppercase or not

>>> print ("#". Join (["A", "B", "C"]) A#b#c # Converts the list to a string, separated by the specified delimiter

>>> print ("ABCD". Lower ()) ABCD # Uppercase to lowercase >>> print ("ABCD". Upper ()) ABCD # lowercase to uppercase

>>> print ("Bcadeafgh". Split ("a")) [' BC ', ' de ', ' FGH '] # Specify delimiter to convert content to list

This article from "12031302" blog, declined reprint!

Python Basics-The next day