Python Best Practices

import json
def f(d,t=[]):
    for i in range(len(d)):
        if d[i]['m']>=40 and d[i]['m']!=None:
            t.append(d[i]['n'])
    return t
x=json.loads('[{"n":"Asha","m":91},{"n":"Ravi","m":35}]')
print(f(x))
print(f(x))

"""Find students who passed an exam."""
import json

PASS_MARKS = 40


def passed_students(results: list[dict], pass_marks: int = PASS_MARKS) -> list[str]:
    """Return names of students whose marks are at least pass_marks."""
    return [r["name"] for r in results if r.get("marks") is not None and r["marks"] >= pass_marks]


def main() -> None:
    results = json.loads('[{"name": "Asha", "marks": 91}, {"name": "Ravi", "marks": 35}]')
    print(passed_students(results))
    print(passed_students(results))


if __name__ == "__main__":
    main()

students = ["Asha", "Ravi", "Neha"]
marks = [91, 58, 76]

# 1. enumerate instead of range(len())
for rank, name in enumerate(students, start=1):
    print(rank, name)

# 2. zip to walk two lists together
report = {name: m for name, m in zip(students, marks)}
print(report)

# 3. f-strings with formatting
fee = 12500.5
print(f"Fee: ₹{fee:,.2f} | Pass rate: {2/3:.0%}")

# 4. truthiness instead of len(x) == 0
pending = []
if not pending:
    print("No pending fees")

# 5. dict.get with a default
print(report.get("Kabir", "absent"))

# 6. unpacking
first, *others = students
print(first, others)

# bad: file stays open if an error happens before close()
f = open("notes.txt", "w", encoding="utf-8")
f.write("Revise loops\n")
f.close()

# good: closed automatically, even on errors
with open("notes.txt", "a", encoding="utf-8") as f:
    f.write("Practise functions\n")

with open("notes.txt", encoding="utf-8") as f:
    print(f.read().strip())

def read_age(text):
    try:
        age = int(text)
    except ValueError:                    # catch only what you expect
        return None
    if not 5 <= age <= 100:
        raise ValueError(f"age {age} out of range")
    return age

print(read_age("15"), read_age("fifteen"))
try:
    read_age("150")
except ValueError as e:
    print("Error:", e)

from dataclasses import dataclass

@dataclass
class Order:
    item: str
    price: float
    qty: int = 1

    @property
    def total(self) -> float:
        return self.price * self.qty

o = Order("Kaju Katli", 900, 2)
print(o)
print(o.total)

import json
def f(d,t=[]):
    for i in range(len(d)):
        if d[i]['m']>=40 and d[i]['m']!=None:
            t.append(d[i]['n'])
    return t
x=json.loads('[{"n":"Asha","m":91},{"n":"Ravi","m":35}]')
print(f(x))
print(f(x))