python learning path

Because of work, my studies have been stagnant for a long time and I have fallen behind a lot. Really, it is important to learn to persevere. There are too many temptations around us and any difficulty may become a reason to give up. Let yourself keep walking, no matter how small the steps are, as long as you walk, there is hope. Give it to yourself and fight to the end.

Collection

A collection is an unordered, non-repeating data combination. Its main functions are as follows:

• Remove duplication, turn a list into a set, and it will automatically remove duplication

• Relationship testing, test the intersection, difference set, and Union and other relations

Change the list into a set

list_1 = [1,4,5,7,3,6,7,9]
liset_1 = set(list_1)
print(list_1,type(list_1))

>>>

[1, 4, 5, 7, 3, 6, 7, 9]

Process finished with exit cod

Intersection

list_1 = [1,4,5,7,3,6,7,9]
liset_1 = set(list_1)

list_2 = set([2,6,0,66,22,8,4])
print(list_1,list_2)

list_1.intersection(list_2)
print( list_1.intersection(list_2 ))
>>>

[4,6]


Union

list_1 = [1,4,5,7,3,6,7,9]
liset_1 = set(list_1)
list_2 = set([2,6,0,66,22,8,4 ])
print(list_1.union(list_2))
>>>
[0,1,2,3,4,5,6,7,66,9, 8,22]


Difference set

list_1 = [1,4,5 ,7,3,6,7,9]
liset_1 = set(list_1)
list_2 = set([2,6,0,66,22,8,4])
print(list_1. difference(list_2))

>>>

[1,3,5,9,7]

Subset

list_1 = [1,4,5,7,3,6,7,9]
liset_1 = set(list_1)
list_2 = set([2,6,0,66,22,8,4])
print(list_1.issubset(list_2))

>>>

false

parent set

list_1 = [1,4,5,7,3,6,7,9]
liset_1 = set(list_1)
list_2 = set([2 ,6,0,66,22,8,4])
print(list_1.issuperset(list_2))

>>>

false

Symmetric difference set

list_1 = [1,4,5,7,3,6,7,9]
liset_1 = set(list_1)
list_2 = set([2,6,0,66,22,8,4])
print(list_1.issubset(list_2))

>>>

[0,1,2,66,3,5,7,9,22]

##It is judged that there is no intersection

print("-----------")

list_3 = set([1,3,7])

##list_4 = set([5,6,8])

print(list_3.isdisjoint(list_4))

>>>

true

Of course, the operation can also be completed using symbols:

s = set([3,5, 9,10]) #Create a set of values ​​

t = set("Hello") #Create a set of unique characters

a = t | s #The union of t and s

b = t & s #The intersection of t and s

c = t – s # Find the difference set (The term is in t, but not in s)

d = t ^ s # Symmetric difference set (the term is in t or s, but does not appear in both at the same time)



Basic operations:

t.add('x') # Add an item

s.update([10,37,42]) # Add in s Multiple items



Use remove() to delete one item:

t.remove('H')


len(s)
The length of set

x in s
Test whether x is a member of s

x not in s
Test whether x is not a member of s

s.issubset(t)
s Test whether every element in s is in t

s.issuperset(t)
s >= t
Test whether every element in t is in s

s.union(t)
s | t
Return a new set containing every element in s and t

s.intersection(t)
s & t
Return a new set containing common elements in s and t

s.difference(t)
s - t
Return a new set containing elements that are in s but not in t

s.symmetric_difference(t)
s ^ t
Return a new set containing s and t Unrepeated elements

s.copy()
Returns a shallow copy of set "s"

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