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May 20th, 2019

## Python Sets

Sets are an unordered collection of unique elements. We can construct them by using the set() function. Let’s go ahead and make a set to see how it works.

### Set and Booleans

There are two other object types in Python that we should quickly cover:

• Sets
• Booleans

### Creating a Set

Sets can be created with set constructor or by directly defining the values in a {} brackets

```a1 = set(),#list()
b2 = {1,2,3}
print(type(a1)
print(type(b2))
<class 'tuple'>
<class 'set'>
```

### Various methods in Set

• membership “in”
• isdisjoint
• subset
• propersubset
• superset
• proper superset
• union
• intersection
• difference
• intersection_update
• difference_update
• symmetric_difference_update
• copy
• pop
• remove
• clear

### 1. membership “in”

#### Example

a = {1,2,3,4,5} #a=1,2 #print(type(a)) b= {4,5,6}

c ={6,7,8}

d= {6,7,9,10,11 }

e={0,1,6,7,11,22,33}

f= {1,2,3,6,7,8}

ab ={1,2, 3, 4, 5}

aa= {“ab”,”bc”,”de”} z =4

#print(len(a)) print(z in b) print(“######################”) #checking conditions

print(“checking membership of c in ab code: c not in ab : result ={0}”.format(z not in ab)) print(“######################”)

True

######################

checking membership of c in ab code: c not in ab : result =False

######################

### 2.Isdisjoint

#### Example

print(“checking if set a and ab are disjoint a is disjoint to ab code:

a.isdisjoint(ab):result: {0} “.format(a.isdisjoint(ab)))

print(“######################”)

checking if set a and ab are disjoint a is disjoint to ab code: a.isdisjoint(ab): result: False

######################

### 3. subset

#### Example

print(“check if all the members of a are members of set ab code:-
a.issubset(ab): result – {0}”.format(a.issubset(ab)))
print(“######################”)
print(“check if all the members of a are members of set ab, , using symbol
code: a <= ab : result- {0}”.format(a <= ab))
print(“check if all the members of a are members of set ab and not equals to set ab ie proper subset
code: a < ab : result – {0}”.format(a < ab))
print(“######################”)
check if all the members of a are members of set ab
code:- a.issubset(ab): result – True
######################
check if all the members of a are members of set ab, , using symbol code:
a <= ab : result – True
check if all the members of a are members of set ab and not equals to set ab ie proper subset
code: a < ab : result – False

### 4. propersubset

 print(“check if all the members of a are members of set ab, here ab is called as superset of a code: ab.issuperset(a) : result – {0} “.format(ab.issuperset(a))) print(“check if all the members of a are members of set ab, here ab is called as superset of a, using symbol code: ab >= a result: – {0}”.format(ab >= a)) print(“######################”) print(“check if all the members of a are members of set ab, here ab is called as superset of a, and is a proper superset code: ab > a result: – {0}”.format(ab > a))

### 5.Union

#### Example

print(“Union or combining elements from two sets code: a.union(b) : result: {}”.format(a.union(b)))

print(“Union or combining elements from two sets – using symbol code: a|b

:result: {}”.format(a|b)) print(“######################”)

### 6.Intersection

#### Example

print(“finding the common items between two sets code: a.intersection(b)

result: – {0}”.format(a.intersection(b)))

print(“finding the common items between two sets -using symbol code: a & b

result: – {0}”.format(a&b)) print(“######################”)

### 7.Difference

#### Example

print(“find the difference between two sets code: a.difference(b) {0}”.format(a.difference(b)))

print(“find the difference between two sets, a -b code: a-b : result: – {0} “.format(a-b))

#print(“udpating one set with elements in other set code: c.update(b) – result {0}”.format(c.update(b))) print(“######################”)

#c|=b

print(“C set is {0} “.format(c)) print(“D set is {0} “.format(d))

print(“intersection update between c and d: code: d.intersection_update(c)

:result – {0}”.format(d.intersection_update(c))) #c &= d

print(“C set is {0} “.format(c)) print(“D set is {0} “.format(d))

find the difference between two sets code: a.difference(b) {1, 2, 3}

find the difference between two sets, a -b code: a-b : result: – {1, 2, 3}

######################

C set is {8, 6, 7} D set is {6, 7}

intersection update between c and d: code: d.intersection_update(c) : result – None

C set is {8, 6, 7} D set is {6, 7}

### 8. Difference_update

#### Example

print(“C set value is {0} “.format(c)) print(“E set value is {0} “.format(e))

print(“difference updated between e and c code: e.difference_update(c) : result – {0}”.format(e.difference_update(c)))

print(“E set becomes {0} “.format(e)) print(“######################”)

C set value is {8, 6, 7}

E set value is {0, 1, 33, 6, 7, 11, 22}

difference updated between e and c code: e.difference_update(c) : result – None

E set becomes {0, 1, 33, 11, 22}

### 9. intersection_update

#### Example

print(“D set becomes {0} “.format(d)) print(“######################”)

#

#print(“intersection update between c and d: code: d.intersection_update(c)

:result – {0}”.format(d.intersection_update(c)))

# print(“D set becomes {0} “.format(d))

#

#

print(“B set value is {0} “.format(b)) print(“C set value is {0} “.format(c)) print(“D set value is {0} “.format(d))

print(“difference updated between b and d , updates the code: b.difference_update(d) : result – {0}”.format(b.difference_update(d))) print(“B set becomes {0} “.format(b))

#print(“difference updated between b and c , updates the using the symbol: b -= c : result – {0}”.format(b -= c))

print(“B set becomes {0} “.format(b)) print(“######################”)

D set becomes {6, 7}

######################

B set value is {4, 5, 6} C set value is {8, 6, 7} D set value is {6, 7}

difference updated between b and d , updates the code: b.difference_update(d) : result – None

B set becomes {4, 5} B set becomes {4, 5}

### 10. symmetric_difference_update

#### Example

print(“F set becomes {0} after symmetric difference”.format(f))
print(“A set becomes {0} after symmetric difference”.format(a))
print(“symmetric difference updated between a and f code: a.symmetric_difference_update(f) : result – {0}”.format(a.symmetric_difference_update(f))) print(“A set becomes {0} “.format(a))
print(“doing the operation again”)
a ^= f
print(“F set becomes {0} after symmetric difference”.format(f))
print(“A set becomes {0} after symmetric difference”.format(a)) F set becomes {1, 2, 3, 6, 7, 8} after symmetric difference
A set becomes {1, 2, 3, 4, 5} after symmetric difference symmetric difference updated between a and f code: a.symmetric_difference_update(f) : result – None
A set becomes {4, 5, 6, 7, 8}
doing the operation again
F set becomes {1, 2, 3, 6, 7, 8} after symmetric difference A set becomes {1, 2, 3, 4, 5} after symmetric difference

### 11.Copy

#### Example

print(aa)
z= aa.copy()
print(“copying to another variable z {0}”.format(z))
{‘bc’, ‘ab’, ‘de’}
copying to another variable z {‘bc’, ‘ab’, ‘de’}

#### Example

print(“add condition result {0}”.format(aa))
print(“add condition result {0}”.format(aa))
print(“add condition result {0}”.format(aa))
#aa.sort()
print(“add condition result {0}”.format(aa))
print(“add condition result {0}”.format(aa)) add condition result {‘bc’, ‘ab’, ‘xy’, ‘de’}
add condition result {‘bc’, ‘de’, ‘xy1’, ‘xy’, ‘ab’}
add condition result {‘bc’, ‘de’, ‘xy1’, ‘xy’, ‘ab’, ‘ay’}
add condition result {‘bc’, ‘de’, ‘xy1’, ‘xy’, ‘ab’, ‘ay’, ‘ay1’}
add condition result {‘bc’, ‘de’, ‘xy1’, ‘abc’, ‘xy’, ‘ab’, ‘ay’, ‘ay1’}

### 13. pop

#### Example

aa.pop()
print(“pop condition result {0}”.format(aa))
pop condition result {‘de’, ‘xy1’, ‘abc’, ‘xy’, ‘ab’, ‘ay’, ‘ay1’}

### 14. Remove

#### Example

aa.remove(“ab”)
print(“remove condition result {0}”.format(aa))
KeyError  Traceback (most recent call last)
<ipython-input-150-16d506463ffa> in <module>()
aa.remove(“ab”)
print(“remove condition result {0}”.format(aa))

KeyError: ‘ab’