Welcome to code review. #Style Check PEP0008 the official Python style guide for maintaining code within Python acceptable standards.

#Code

Welcome to code review.

Style

Check PEP0008 the official Python style guide for maintaining code within Python acceptable standards.

Code

• Functions: A function is a block of code which only runs when it is called. You can pass data, known as parameters, into a function. A function can return data as a result. Since this a bad use of classes because a class is usually used for an object with multi-attributes and multi-methods and this is not the case here, you might use a regular function.
• Augmented assignment: Python supports augmented assignments ex: i=i-1 is i -= 1, count=count+1 is count += 1 ...
• Semi-columns: are for combining multiple short statements on the same line, this j=0; (line 15) is an invalid use of semi-columns.
• Comparison to True and False: is usually done using if something: and if not something_else: ex: flagarray[i]==False: is if not flag_array[i]:. Non-empty sequences and non-zero variables evaluate to True ex: if len(ca)>0: is if ca:
• Inefficiency: If you need to print duplicates of a list you shouldn't be entering each of the list members manually (what if you have a list of size 10,000,000 items? will you be manually entering one by one?)
• Counter() You could use counter dict from the collections library for counting list members

• Functions: A function is a block of code which only runs when it is called. You can pass data, known as parameters, into a function. A function can return data as a result. Since this a bad use of classes because a class is usually used for an object with multi-attributes and multi-methods and this is not the case here, you might use a regular function.
• Augmented assignment: Python supports augmented assignments ex: i=i-1 is i -= 1, count=count+1 is count += 1 ...
• Semicolons: are for combining multiple short statements on the same line, this j=0; (line 15) is an invalid use of semicolons.
• Comparison to True and False: is usually done using if something: and if not something_else: ex: flagarray[i]==False: is if not flag_array[i]:. Non-empty sequences and non-zero variables evaluate to True ex: if len(ca)>0: is if ca:
• Inefficiency: If you need to print duplicates of a list you shouldn't be entering each of the list members manually (what if you have a list of size 10,000,000 items? will you be manually entering one by one?)
• Counter() You could use counter dict from the collections library for counting list members

from collections import Counter
def get_duplicates(numbers: list):
 """Return list duplicates."""
 return {item for item in numbers if Counter(numbers)[item] > 1}
if __name__ == '__main__':
 list_of_duplicates = [1, 2, 2, 3, 4, 3, 5, 2, 7, 1, ]
 print(get_duplicates(list_of_duplicates))

from collections import Counter
def get_duplicates(numbers: list):
 """Return list duplicates."""
 num_duplicates = Counter(numbers)
 return {item for item in num_duplicates if num_duplicates[item] > 1}
if __name__ == '__main__':
 list_of_duplicates = [1, 2, 2, 3, 4, 3, 5, 2, 7, 1, ]
 print(get_duplicates(list_of_duplicates))