A collection of Python basics

Python basic Three:
First, sort data types:
Mutable and immutable:
1. Variable: list, dictionary
2, immutable: strings, tuples, numbers
Access Order:
1. Direct Access: Digital
2. Sequential access: String, list, tuple
3. Mapping: Dictionary
Number of elements to store:
1. Container type: list, tuple, dictionary
2. Atomic type: Number, string

Two, set
Characteristics:
1. Composition of different elements
2, is disorderly
3. The elements in the collection must be immutable types (numbers, strings, tuples)
4. How to define the collection: Test = {' Xyy ', ' Xyyp ', 1,2,3,4} or test = set (' XYY ')

Three, set function:
Add () Adds an element to the collection and can only add one element at a time

Test = {' Xyy ', ' Xyyp ', 1,2,3,4}test.add (5) test.add (' Xyp ') print (test)

Results:

Clear () empties the contents of the collection

Test = {' Xyy ', ' Xyyp ', 1,2,3,4}test.clear () print (test)

Results:

Copy () copies a new set of contents

Test = {' Xyy ', ' xyyp ', 1,2,3,4}n = Test.copy () print (n)

Results:

Pop () deletes a random element

Test = {' Xyy ', ' Xyyp ', 1,2,3,4}test.pop () print (test)

Results:

Remove () deletes the specified content and will error if the specified content does not exist

Test = {' Xyy ', ' Xyyp ', 1,2,3,4}test.remove (' Xyyp ') print (test)

Results:

Discard () deletes the specified content and does not error if the specified content does not exist

Test = {' Xyy ', ' Xyyp ', 1,2,3,4}test.discard (' XYY ') test.discard (' XYYFG ') print (test)

Results:

Update () adds multiple elements to the collection, which is a bit more powerful than add

Test = {' Xyy ', ' xyyp ', ' Xyp '}test.update (' Jony ', ' Tom ')//Add a tuple then the result is the complete string test.update (' Jony ', ' Tom ')// If you add a string, the result is a single character print (test)

Results:

Isdisjoint () determines that two sets have the same element as wood, and none is true (true)

Test1 = {' Xyy ', ' xyyp ', ' xyp '}test2 = {' Xyyx ', ' xypc '}n = Test1.isdisjoint (test2)//Test1 and test2 do not have the same element print (n)

Results:

Iv. Python Set-relational operations:
1, Intersection: intersection () will output two sets of the same content

Test1 = {' Xyy ', ' xyyp ', ' xyp '}//define two sets, two sets have the same and different elements test2 = {' Xyy ', ' xyp ', ' fg '}n = test1.intersection (test2) print (n)

Results:

Or:

Test1 = {' Xyy ', ' xyyp ', ' xyp '}test2 = {' Xyy ', ' xyp ', ' fg '}n = test1&test2//intersection can use & symbol instead of print (n)

Results:

2 Unions: Union () outputs different contents of two sets and synthesizes a collection

Test1 = {' Xyy ', ' xyyp ', ' xyp '}test2 = {' Xyy ', ' xyp ', ' fg '}n = test1.union (test2) print (n)

Results:

Or:

Test1 = {' Xyy ', ' xyyp ', ' xyp '}test2 = {' Xyy ', ' xyp ', ' fg '}n = test1|test2//a vertical bar (|) means union this function print (n)

3, Difference set: Difference () The first set minus the second set to the first set is different from the second set of an element, which in turn means

Test1 = {' Xyy ', ' xyyp ', ' xyp '}test2 = {' Xyy ', ' xyp ', ' fg '}N1 = test1.difference (test2)//test1 collection minus test2 set n2 = Test2.difference (test1)//test2 collection minus Test1 collection print (N1,N2)

Results:

Or:

Test1 = {' Xyy ', ' xyyp ', ' xyp '}test2 = {' Xyy ', ' xyp ', ' fg '}N1 = test1-test2//with a minus sign (-) instead of Differenceprint (n1) N2 = Test2-test1print (N2)

Results:

4, cross-complement set: Symmetric_difference () Only take two sets of different parts

Test1 = {' Xyy ', ' xyyp ', ' xyp '}test2 = {' Xyy ', ' xyp ', ' fg '}N2 = test1.symmetric_difference (test2) print (N2)

Results:

Or:

Test1 = {' Xyy ', ' xyyp ', ' xyp '}test2 = {' Xyy ', ' xyp ', ' Tom '}n = Test1^test2//symmetric_difference () can be used instead of print (n)

Results:

5. Subset: Issubset () determine who is a subset of WHO

Test1 = {' Xyy ', ' xyyp ', ' xyp '}test2 = {' Xyy ', ' xyp '}n = Test2.issubset (test1)//two sets have the same part, but the second one is less than the first element, So the second one is a subset of the first print (n)

Results:

6. Parent set: Issuperset () judge who is the parent of the set

Test1 = {' Xyy ', ' xyyp ', ' xyp '}test2 = {' Xyy ', ' xyp '}n = Test1.issuperset (test2)//two sets have the same part, but the first one is more than the second element, So the first one is the second parent set print (n)

Results:

A collection of Python basics