List dictionary tuple collection data structure in Python

• 2020-04-02 14:20:47
• OfStack

This article summarizes the list, dictionary, tuple and collection data structure in Python in detail. Share with you for your reference. Specific analysis is as follows:

List:

``shoplist = ['apple', 'mango', 'carrot', 'banana']``

Dictionary:
``di = {'a':123,'b':'something'}``

Collection:
``jihe = {'apple','pear','apple'}``

Tuples:
``t = 123,456,'hello'``

List 1.

Empty list: a=[]

Function method:

``````          a.append(3)     　　>>>[3]
a.extend([3,4,5])     　　>>>[3,3,4,5]    # Add a list sequence
a.insert(1,'hello')    　　  >>>[3,'hello',3,4,5]
a.remove(3)        　　　  >>>['hello',3,4,5] # Delete the first one that appears 3 , there is no 3 Is an error
a.pop()        　　　　　　>>>['hello',3,4]
a.pop(0)        　　　　　　>>>[3,4]
a.index(4)       　　 >>>1    # Returns the first one that appears 4 The subscript
a.count(3)        　　>>>1    # List element 3 The number of
a.sort        >>>[3,4]    # The sorting
a.reverse()        >>>[4,3]    # trans ``````

Delete element method:

``````        a.remove(3)    # Deletes an element by value, removing the first element as an argument
a.pop()       # The element is deleted by subscript, the last value of the list is deleted by default, and the element with parameter is deleted by subscript
del a[0]       # Delete an element by subscript,
del a[2:4] # delete a Table subscript for 2,3 The elements of the
del a[:]   # delete a List all elements
del a       # Delete the list ``````

List derivation:

``````        vec = [2,4,6]
[3*x for x in vec if x<6]    >>>[6,12]    3*2,3*4
vec2 = [1,2,3]
[x*y for x in vec for y in vec2]    >>>[2,4,6,4,8,12,6,12,18]``````

Nested list derivation:

``````        mat = [
[1,2,3],
[4,5,6],
[7,8,9]
]
print ([[row[i] for row in mat] for i in [0,1,2]])
>>>[[1, 4, 7], [2, 5, 8], [3, 6, 9]]``````

Thinking: what's the difference between the results of list (zip(mat)) and list (zip(*mat)

2. A tuple

Null tuple: t = ()
Tuple assignment: t = (123,345)
T [0]                 > > > 123
3. The dictionary

``````    d = {'Jack':'jack@mail.com','Tom':'Tom@main.com'}
d['Jack']    　　　　　　　　>>>'jack@mail.com
d['Jim'] = 'Jim@sin.com'    >>>{'Jim': 'Jim@sin.com', 'Jack': 'jack@mail.com', 'Tom': 'Tom@main.com'}
del d['Jim']    >>>{'Jack': 'jack@mail.com', 'Tom': 'Tom@main.com'}
list(d.keys())    # Returns an unordered list of all the keywords in the dictionary
sorted(d.keys()) # A sorted list of all the keywords in a dictionary is returned
dict()    # The constructor can be written directly from key-value Create a dictionary in pairs
dict([('Tim',123),('Tiny',234)])    >>>{'Tiny': 234, 'Tim': 123}``````

Derivation to create a dictionary:

``````        {d2:d2+'@main.com' for d2 in list(d.keys())}
>>>{'Jack': 'Jack@main.com', 'Tom': 'Tom@main.com'}``````

Exercise: loop output key value pairs in the dictionary:
``````        for name,email in d.items():
print(name,email)``````

Collection of 4.

Empty set: A = set() does to create an empty set, you must use set()

Presentation:

``````    basket = {'apple','orange','apple'}    >>>{'orange', 'apple'}    # Note that duplicate elements show only one

Mathematical operation of set:

``````        a = set('ababcdabca')        >>>{'c', 'b', 'a', 'd'}
b = {'a','b','m'}            >>>{'b', 'a', 'm'}
a - b        >>>{'c', 'd'}
b - a        >>>{'m'}
a | b        >>>{'c', 'd', 'b', 'a', 'm'}
a & b        >>>{'a','b'}
a ^ b        >>>{'c','d','m'}``````

Set derivation formula:

``       {x for x in a if x not in 'ab'}    >>>{'c','d'}``