Python learning 2-python simple data types

Python Simple data type

1. List

   list creation, using []

   A_list = [' A ', ' B ', ' C ']

   Print A_list

   Print A_list[0] #a

   If you go to the last element of the list, in addition to calculating the index location, you can also use-1

   Print A_list[-1] #c

   And so on, you can get the bottom 2nd, the bottom 3rd one.

   Print A_list[-2] #b

   Print A_list[-3] #a

   The addition of the list element

   A_list.append (' d ') #增加到末尾

   A_list.insert (1, ' e ') #增加到指定位置

   A_list.extend ([' F ', ' g ', ' h ') #将两个个对象的元素加到该list的末尾

   A_list*3 #使用乘法扩展list

   Delete of list element

   Del A_list[1] #删除指定元素

   Del a_list #删除整个list

   A_list.pop () #删除最后一个元素. To delete the specified index position element, pop (i)

   A_list.remove (' a ') #删除首次出现的指定元素

   Substitution of list elements

   A_list[1] = ' Z ' #直接赋值给对应索引位置

   The data type of the list element can be different

   A_list = [' Apple ', ' 123 ', True] #True和False首字母要大写

   The list element can also be another list

   A_list = [' Apple ', ' orange ', [' Python ', 123], 321]

   Print Len (a_list) #4

   List element Access and Count

   accessing directly using indexed locations

   A_LIST[1]

   Gets the index position of the first occurrence of the specified element

   A_list.index (' a ')

   Gets the number of occurrences of the specified element in the list

   A_list.count (' a ')

   For Yuanju, string, and range

   Range (Ten). Count (3) #1

   (2,2,2,4). Count (2) #3

   (' A ', ' B ', ' C ', ' a '). Count (' a ') #2

   Determines whether the specified element is in the list

   ' A ' in a_list

   Slicing operations

   x = Range (10,100)

   x[::] #全取

   X[::-1] #倒着全取

   X[::2] #从头每两个取一个

   X[::-2] #倒着每两个取一个

   X[1::2] #从位置1每两个取一个

   X[3:6] #取指定范围

   X[:10:2] #前10个中每两个取一个

   List sort

   A_list = [1,2,3,4,5,6]

   Import Random

   Random.shuffle (a_list) #打乱顺序

   A_list.sort () #默认升序

   A_list.sort (reverse = True) #降序排序

   You can also use sorted () to sort, unlike the sort () directly for list modifications, sorted () returns a new list and does not manipulate the original list

   b = Sorted (a_list)

   Reverse the list element

   A_list.reverse ()

   You can also sort by reversed (), unlike reverse (), which changes directly to the list, reversed () returns a new list and does not manipulate the original list

   Newa = Reversed (a)

2. tuple

   Tuple and list are very similar, but the tuple cannot be modified once initialized, he does not have append (), insert () method. The method to get the element is the same as list, but cannot be assigned to another element

   Creating a tuple ()

   a_tuple = (' A ', ' B ', ' C ')

   b_tuple = (' A ',)

   < Span style= "font-size:10pt" Use the tuple () function to convert other types of sequences to Ganso

   a = tuple (' ABCDEFG ')

   Alist = [1,2,3,4, ' a ']

   tuple (alist)

   &NBSP;

4. Dict

   The dictionary is an unordered, variable sequence of key-value pairs, and each element in the dictionary contains two parts: Key and value, using curly braces {}.

   Creation of dictionaries

   D = {' Michael ': Up, ' Bob ': +, ' Tracy ': 85}

   Print d[' Michael '] #95

Determine if key exists

print ' Bob ' in D #True

print ' Bob ' in D #False

Read from Dict

d[' Michael '] #95

can also be obtained by means of a GET, if key does not exist, returns none or the value specified by itself

D.get (' Michael ') #95

D.get (' Mi ',-1) #-1

Dict items () can return the dictionary's "Key-value" list

For item in D.items ():

Print (item)

For key in D:

Print (key)

For key, value in D.items ():

Print (key, value)

Increase of dict elements

When the key is subscript, if the keys exist, then modify the value, if not present, add a heap of key-value

d[' Michael '] = #将Michael的值从95修改为96

d[' Jack '] = #增加一对key-value

Dict Delete

To delete a pair of key values, use POP (key)

D.pop (' Michael ')

1. Set

   Each element of the set is unique, using curly braces {}

   Creation of Set

   A ={1,2}

   Print a #set ([+])

   Creating a set can also use the set () function to convert the list, Ganso to set, and if duplicate elements exist in the original data, only one

   A_set =set (Range (8,14))

   Print A_set

   Increase of Set

   A.add (3)

   Print a #set ([+])

   Operation of Set

   S1 = set ([+])

   S2 = set ([2,3,4])

   Print S1&s2 #交集

   Print S1|s2 #并集

Python learning 2-python simple data types