How to use the set method in Python

1. Preface

In Python, set is a set data type, representing an unordered and non-repeating set. The set() method can be used to create an empty collection or to convert other iterable objects into a collection. Unlike other Python data types, a set does not have an index and its elements cannot be accessed by index, but there are methods that can be used to manipulate and access the elements in the set. Create an empty collection using the set() method

2. Detailed explanation of the commonly used set() method

1.add(): Add an element to the set collection

# add（）语法如下：
set.add(elmnt)

# 案例如下：
set1 = {1,2,3}
set1.add(4)
print(set1)

# 输出结果如下
{1, 2, 3, 4}

2.clear(): Remove all elements from the set collection

# clear()语法如下:
set.clear()
# 案例如下：
set1 = {1, 2, 3}
set1.clear()
print(set1)
# 输出结果如下：
set()

3.copy(): Used to copy a collection, use copy( ) method creates a complete copy of the original collection, and operations on the copied collection will not affect the original collection.

# 语法如下：
new_set = old_set.copy()
# 案列如下：
set1 = {1, 2, 3}
set2 = set1.copy()
set2.add(4)
print(set1)
print(set2)
# 输出结果如下：
{1, 2, 3}
{1, 2, 3, 4}
# 首先，我们创建了一个原始集合，然后使用copy方法创建了一个新集合，并在新集合中添加了一个元素4，
# 最后，我们打印了原始集合和复制出的新集合，可以看到两个集合互不影响。

4.difference(): This method is used to return the difference set of the set, that is, the returned set elements are included in the first set, but not in the second set ( method parameters).

# 语法如下：
set1.difference(set2)
# 案例如下：
set1 = {1, 2, 3}
set2 = {2, 3, 4}
print(set1.difference(set2))
# 输出结果如下：
{1}

5.difference_update(): method is used to remove elements that exist in both collections

difference_update() method and difference() method The difference is that the difference() method returns a new collection with the same elements removed, while the difference_update() method directly removes elements from the original collection without returning a value.

# 语法如下：
set1.difference_update(set2)
# 案例如下：
set1 = {1, 2, 3, 4, 5}
set2 = {2, 3, 4}
set1.difference_update(set2)
print(set1)
# 输出结果如下
{1, 5}

6.discard() method syntax: The discard() method is used to remove specified collection elements.

This method is different from the remove() method because the remove() method will cause an error when removing a non-existent element, while the discard() method will not.

# 语法如下：
set.discard(value)
# 案例如下
set1 = {1, 2, 3}
set2 = {2, 3, 4}
set1.discard(2), set2.discard(3)
print(set1, set2)
# 输出结果如下：
{1, 3} {2, 4}
# 删除不存在元素，不会引发任何异常
set1.discard(4)
print(set1)
# 输出结果如下
{1, 2, 3}

7. The intersection() method is used to return elements contained in two or more sets, that is, the intersection.

# 语法如下：
set1.intersection(set2, set3, ...)
# 案例如下：
set1 = {1, 2, 3}
set2 = {2, 3, 4}
set3 = set1.intersection(set2)
print(set3)
# 输出结果如下：
{2, 3}

8. The intersection_update() method is used to obtain overlapping elements in two or more sets, that is, to calculate the intersection.

The intersection_update() method is different from the intersection() method because the intersection() method returns a new set, while the intersection_update() method removes non-overlapping elements on the original set.

# 语法如下：
set1.intersection_update(set2, set3, ...)
# 案例如下:
set1 = {1, 2, 3}
set2 = {2, 3, 4}
set1.intersection_update(set2)
print(set1)
# 输出结果如下：
{2, 3}

9.isdisjoint() method is used to determine whether two sets contain the same elements. If not, it returns True, otherwise it returns False.

# 语法如下：
set1.isdisjoint(set2)
# 案例如下：
set1 = {1, 2, 3}
set2 = {2, 3, 4}
set3 = {4, 5, 6}
print(set1.isdisjoint(set2))
print(set3.isdisjoint(set1))
# 输出如果如下：
False
True

10.issubset() method is used to determine whether a set is a subset of another set. If all elements of one set are contained in another set, return True if so, otherwise return False

# 语法如下：
set1.issubset(set2)
# 案例如下：
set1 = {1, 2, 3}
set2 = {2, 3, 4}
set3 = {1, 2, 3, 4}
print(set1.issubset(set2))
print(set1.issubset(set3))
# 输出结果如下：
False
True

11.issuperset() method is used to determine whether one set is another set A superset of a set. If a set contains all elements of another set, the set is a superset of the other set, and the issuperset() method returns True; otherwise, it returns False.

# 语法如下：
set1.issuperset(set2)
# 案例如下：
set1 = {1, 2, 3}
set2 = {2, 3, 4}
set3 = {1, 2, 3, 4}
print(set1.issuperset(set2))
print(set3.issuperset(set1))
# 输出结果如下：
False
True

12.pop() method is used to randomly remove an element and return the value of the element.

# 语法如下：
set.pop()
# 案例如下：
# 随机移除一个元素：
set1 = {1, 2, 3, 4}
set1.pop()
print(set1)
# 结果如下：
{2, 3, 4}
# 输出返回值：
set1 = {1, 2, 3, 4}
print(set1.pop())
# 结果如下：
1

13.remove() method is used to remove specified elements from the collection.

This method is different from the discard() method because the remove() method will cause an error when removing a non-existent element, while the discard() method will not.

# 语法如下：
set.remove(item)
# 案例如下：
set1 = {1, 2, 3, 4}
set1.remove(4)
print(set1)
# 输出结果如下：
{1, 2, 3}

14. The symmetric_difference() method returns a set of non-duplicate elements in the two sets, that is, it will remove the elements that exist in both sets, that is, it will return the elements that are different from each other in the two sets. Collection of elements.

# 语法如下：
set1.symmetric_difference(set2)
# 案例如下：
set1 = {1, 2, 3}
set2 = {2, 3, 4}
print(set1.symmetric_difference(set2))
# 输出结果如下：
{1, 4}

15. The symmetric_difference_update() method removes the same elements from the current collection in another specified collection, and inserts different elements from another specified collection into the current collection.

# 语法如下：
set1.symmetric_difference_update(set2)
# 案例如下：
set1 = {1, 2, 3}
set2 = {2, 3, 4, 5}
set1.symmetric_difference_update(set2)
print(set1)
# 输出结果如下：
{1, 4, 5}

16. The union() method returns the union of two sets, which contains the elements of all sets. Duplicate elements will only appear once.

# 语法如下：
set1.union(set2)
# 案例如下：
# 合并两个集合，重复元素只会出现一次：
set1 = {1, 2, 3}
set2 = {2, 3, 4}
print(set1.union(set2))
# 输出结果如下：
{1, 2, 3, 4}
# 合并多个集合：
set1 = {1, 2, 3}
set2 = {2, 3, 4}
set3 = {3, 4, 5, 6, 7}
print(set1.union(set2, set3))
# 输出结果如下:
{1, 2, 3, 4, 5, 6, 7}

17.update(): method is used to modify the current collection. You can add new elements or collections to the current collection. If the added element already exists in the collection, then the Elements will appear only once, and duplicates will be ignored.

# 语法如下：
set1.update(set2)
# 案例如下：
set1 = {1, 2, 3}
set2 = {2, 3, 4}
set1.update(set2)
print(set1)
# 结果如下：
{1, 2, 3, 4}

3. Summary

1. Create an empty collection

It is very simple to create an empty collection using the set() method. Simply call the set() method to create an empty set object.

# 例子：
set_data = set()
print(set_data)
# 输出结果如下:
set()

2. Convert iterable objects to sets

The set() method can also convert other iterable objects (such as lists, tuples, and strings) into sets.

# 案例：
list1 = [1, 2, 3, 4, 5]
set1 = set(list1)
print(set1)
tuple1 = (1, 2, 3, 4, 5)
set2 = set(tuple1)
print(set2)
str1 = "Hello, world!"
set3 = set(str1)
print(set3)
# 输出结果如下：
{1, 2, 3, 4, 5}
{1, 2, 3, 4, 5}
{'d', 'H', 'o', ',', 'l', 'e', '!', 'r', 'w', ' '}

3. Other uses of the set() method

Split the string into individual characters and store them in a set.

# 例子：
str2 = "Python"
set4 = set(str2)
print(set4)
# 输出结果：
{'h', 't', 'o', 'n', 'P', 'y'}

4. Conclusion

Collection objects have many built-in methods for adding, deleting, merging, comparing, and manipulating elements in the collection. The following are some common methods of set objects:

• add(): used to add a single element to the set.

• clear(): Used to clear all elements in the collection.

• copy(): Used to create a copy of the collection.

• difference(): Used to return the difference between two sets.

• difference_update(): Used to delete elements in a collection that are the same as another collection.

• discard(): Used to delete the specified element in the collection.

• intersection(): Used to return the intersection of two sets.

• intersection_update(): Used to retain the same elements in a collection as another collection.

• isdisjoint(): Used to determine whether two sets have no common elements.

• issubset(): Used to determine whether a set is a subset of another set.

• issuperset(): Used to determine whether a set is a superset of another set.

• pop(): Used to randomly remove an element.

• remove(): Used to remove the specified element from the collection.

• symmetric_difference(): Used to return the symmetric difference of two sets.

• symmetric_difference_update(): Used to retain non-common elements in the set and delete common elements.

• union(): Used to return the union of two sets.

• update(): Used to add elements from one collection to another collection.

These methods can be used by calling the method name on the collection object and providing the necessary parameters. For example, use the add() method to add a single element to a collection, and use the update() method to add elements from one collection to another.

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