Python | Difference in Record Lists

Sometimes, while working with data, we may have a problem in which we require to find the difference records between two lists that we receive. This is a very common problem and records usually occurs as a tuple. Let’s discuss certain ways in which this problem can be solved. 

Method #1 : Using list comprehension

List comprehension can be opted as method to perform this task in one line rather than running a loop to find the difference elements. In this, we just iterate for single list and check if any element occurs in other one. 

Python3

# Python3 code to demonstrate working of
# Difference in Record Lists
# Using list comprehension

# Initializing lists
test_list1 = [('gfg', 1), ('is', 2), ('best', 3)]
test_list2 = [('i', 3), ('love', 4), ('gfg', 1)]

# Printing original lists
print("The original list 1 is : " + str(test_list1))
print("The original list 2 is : " + str(test_list2))

# Intersection in Tuple Records Data
# Using list comprehension
res = [ele1 for ele1 in test_list1 for ele2 in test_list2 if ele1 == ele2]
res = list(set(res) ^ set(test_list1))

# Printing result
print("The difference of data records is : " + str(res))

Output : 

The original list 1 is : [('gfg', 1), ('is', 2), ('best', 3)]
The original list 2 is : [('i', 3), ('love', 4), ('gfg', 1)]
The difference of data records is : [('best', 3), ('is', 2)]

Time Complexity: O(n*n), where n is the number of elements in the list “test_list”.
Auxiliary Space: O(n*n), where n is the number of elements in the list “test_list”.

Method #2: Using set.intersection() + set operations

This task can also be performed in a smaller way using the generic set intersection. In this, we first convert the list of records to a set and then perform its intersection using intersection(). Then the result is computed by taking the uncommon element of the result from the first list. 

Python3

# Python3 code to demonstrate working of
# Difference in Record Lists
# Using set.intersection() + set operations

# Initializing lists
test_list1 = [('gfg', 1), ('is', 2), ('best', 3)]
test_list2 = [('i', 3), ('love', 4), ('gfg', 1)]

# printing original lists
print("The original list 1 is : " + str(test_list1))
print("The original list 2 is : " + str(test_list2))

# Difference in Record Lists
# Using set.intersection() + set operations
res = list(set(test_list1).intersection(set(test_list2)))
res = list(set(res) ^ set(test_list1))

# printing result
print("The difference of data records is : " + str(res))

Output : 

The original list 1 is : [('gfg', 1), ('is', 2), ('best', 3)]
The original list 2 is : [('i', 3), ('love', 4), ('gfg', 1)]
The difference of data records is : [('best', 3), ('is', 2)]

Method #3: Here is another approach to finding the difference between two lists of records, using the filter() method.

Python3

# Python3 code to demonstrate working of
# Difference in Record Lists
# Using filter() method

# Initializing lists
test_list1 = [('gfg', 1), ('is', 2), ('best', 3)]
test_list2 = [('i', 3), ('love', 4), ('gfg', 1)]

# printing original lists
print("The original list 1 is : " + str(test_list1))
print("The original list 2 is : " + str(test_list2))

# Difference in Record Lists
# Using filter() method
res = list(filter(lambda x: x not in set(test_list2), set(test_list1)))

# printing result
print("The difference of data records is : " + str(res))

Output

The original list 1 is : [('gfg', 1), ('is', 2), ('best', 3)]
The original list 2 is : [('i', 3), ('love', 4), ('gfg', 1)]
The difference of data records is : [('best', 3), ('is', 2)]

Time Complexity: O(n), where n is the length of the test_list1
Auxiliary Space: O(n), as a new list res of length n is created.

Method 4: use a for loop and conditional statements. 

Steps:

1. Initialize two lists of records.
2. Create an empty list to store the difference.
3. Use a for loop to iterate through each record in the first list.
4. Use a nested for loop to iterate through each record in the second list.
5. Check if the record in the first list matches the record in the second list.
6. If the records match, break out of the nested loop and move to the next record in the first list.
7. If the records do not match, append the record to the difference list and move to the next record in the first list.
8. Print the difference list.

Python3

# Python3 code to demonstrate working of
# Difference in Record Lists
# Using for loop and conditional statements

# Initializing lists
test_list1 = [('gfg', 1), ('is', 2), ('best', 3)]
test_list2 = [('i', 3), ('love', 4), ('gfg', 1)]

# printing original lists
print("The original list 1 is : " + str(test_list1))
print("The original list 2 is : " + str(test_list2))

# Difference in Record Lists
# Using for loop and conditional statements
diff_list = []

for record1 in test_list1:
    found_match = False
    for record2 in test_list2:
        if record1 == record2:
            found_match = True
            break
    if not found_match:
        diff_list.append(record1)

# printing result
print("The difference of data records is : " + str(diff_list))

Output

The original list 1 is : [('gfg', 1), ('is', 2), ('best', 3)]
The original list 2 is : [('i', 3), ('love', 4), ('gfg', 1)]
The difference of data records is : [('is', 2), ('best', 3)]

Time Complexity: O(n*m), where n and m are the lengths of the two lists respectively.
Auxiliary Space: O(k), where k is the length of the difference list.

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