Manipulate on a field from a table

Python Help
1

I have four fields in a table
a, b, c, d
I want to update only one field example ‘a’
please guide.

2

tablename.objects.filter(fieldname=value)

is this correct ?

then I want apply “sum” based on filter.
Please guide

3

You are not providing any details, like you code, for people to comment on to help you.
Also when you provide code put it in side code-fences like this:

```
print('Your code like this')
```