Use dictionary comprehension technique.
We have dictionary object having name and percentage of students
>>> marks = {
'Ravi': 45.23,
'Amar': 62.78,
'Ishan': 20.55,
'Hema': 67.20,
'Balu': 90.75
}
To obtain dictionary of name and marks of students with percentage>50
>>> passed = { key:value for key, value in marks.items() if value > 50 }
>>> passed
{'Amar': 62.78, 'Hema': 67.2, 'Balu': 90.75}
To obtain subset of given names
>>> names = { 'Amar', 'Hema', 'Balu' }
>>> lst = { key:value for key,value in marks.items() if key in names}
>>> lst
{'Amar': 62.78, 'Hema': 67.2, 'Balu': 90.75}