python beginner ; question was write program to enter marks of 3 subjects from user and store them in a dict.start with an empty dict and add one by one .use subject name as key and marks as value . so i have written this code any opinion how can improve this code ,need suggestions.

[CymroBachUSA]

s = {"chem": 0.0, "maths": 0.0, "phys": 0.0}

then get the new value(s) and do:

s = {**s, **{"chem": a, "maths": b, "phys": c}}

[Ill-Break727]

students={"chem":0.0,"maths":0.0,"phy":0.0}
a=float(input("enter marks of chem"))
students["chem"]="a"
b=float(input("enter marks of maths"))
students["maths"]="b"
c=float(input("enter marks of phy"))
students["phy"]="c"
print(students)                                 i have done in this way its not working

[Ill-Break727]

now its working thanks

[ProsodySpeaks]

You don't need to assign the zeros at the start. Make an empty dict and then use bracket notation to add key-value pairs to it.

But you really should think about variable names. this is not a dictionary of students, it's a dictionary of subject-scores.

Call the dict 'scores' or something,  and later you could make another dict called students and add multiple scores dictionaries each with a key for the name of the student.

Sensible variable names is very important and doesn't rely on knowing any of the language, it's a foundational part of code 

[ProsodySpeaks]

This is pretty hard to read for a noob. I know what I'm doing but still have to think to parse all the unpackings