एक्सेप्शन्स — टूटी हुई स्थिति को संभालना

numbers = ["10", "twenty", "30"]
total = 0

for text in numbers:
    total += int(text)

print(total)

ValueError: invalid literal for int() with base 10: 'twenty'

numbers = ["10", "twenty", "30"]
total = 0

for text in numbers:
    try:
        total += int(text)
    except ValueError:
        print("skipping", text)

print(total)

skipping twenty
40

try:
    int("twenty")
except ValueError as err:
    print(type(err))
    print(err)

<class 'ValueError'>
invalid literal for int() with base 10: 'twenty'

try:
    int("twenty")
except TypeError:
    print("caught")

ValueError: invalid literal for int() with base 10: 'twenty'

numbers = ["10", "twenty", "30"]
total = 0

for text in numbers:
    try:
        total += int(text)
    except Exception:
        pass

print(total)

40

def get(data, key):
    try:
        return data[key]
    except KeyError:
        return "no such key"
    except IndexError:
        return "no such position"


print(get({"pen": 15}, "pen"))
print(get({"pen": 15}, "bag"))
print(get([1, 2, 3], 9))

15
no such key
no such position

for value in ["10", None, "x"]:
    try:
        print(int(value))
    except (ValueError, TypeError) as err:
        print(type(err).__name__, "-", err)

10
TypeError - int() argument must be a string, a bytes-like object or a real number, not 'NoneType'
ValueError - invalid literal for int() with base 10: 'x'

print(issubclass(FileNotFoundError, OSError))
print(issubclass(ValueError, Exception))
print(issubclass(KeyError, LookupError))
print(issubclass(IndexError, LookupError))

True
True
True
True

try:
    raise FileNotFoundError("gone")
except OSError as err:
    print("caught as OSError:", err)

caught as OSError: gone

def read(text):
    try:
        value = int(text)
    except ValueError:
        print("bad:", text)
        return None
    else:
        print("good:", value)
        return value
    finally:
        print("done with", text)


print(read("10"))
print(read("ten"))

good: 10
done with 10
10
bad: ten
done with ten
None

def risky():
    try:
        return "from try"
    finally:
        print("finally still runs")


print(risky())

finally still runs
from try

def line_total(price, quantity):
    if quantity < 0:
        raise ValueError(f"quantity cannot be negative: {quantity}")
    return price * quantity


print(line_total(15.0, 3))
print(line_total(15.0, -1))

45.0
ValueError: quantity cannot be negative: -1

def parse(text):
    try:
        return int(text)
    except ValueError:
        raise ValueError(f"not a number: {text!r}")


print(parse("10"))
print(parse("ten"))

10
ValueError: not a number: 'ten'

pen,15.0,3
bag,eight,1

ink,120.0,2
clip,5.0

"""एक ऑर्डर फ़ाइल पढ़ें, और किसी पंक्ति के गलत होने पर भी चलते रहें।"""

from pathlib import Path

TAX_RATE = 0.15


def parse_line(raw, number):
    """एक ऑर्डर लाइन लौटाता है, या यह बताते हुए ValueError उठाता है कि कौन सी लाइन गलत थी।"""
    parts = raw.split(",")
    if len(parts) != 3:
        raise ValueError(f"line {number}: expected 3 fields, got {len(parts)}")

    name, price, quantity = parts
    try:
        return name, float(price), int(quantity)
    except ValueError as err:
        raise ValueError(f"line {number}: {err}")


def read_order(path):
    """सही लाइनों और शिकायतों को लौटाता है, खराब डेटा के लिए कभी क्रैश नहीं होता।"""
    try:
        text = path.read_text(encoding="utf-8")
    except FileNotFoundError:
        return [], [f"no such file: {path}"]

    lines = []
    problems = []

    for number, raw in enumerate(text.splitlines(), start=1):
        if not raw.strip():
            continue
        try:
            lines.append(parse_line(raw, number))
        except ValueError as err:
            problems.append(str(err))

    return lines, problems


def main():
    lines, problems = read_order(Path("orders.txt"))

    total = 0.0
    for name, price, quantity in lines:
        amount = round(price * quantity * (1 + TAX_RATE), 2)
        total += amount
        print(f"{name:<6} {amount:>9.2f}")

    print(f"{'total':<6} {total:>9.2f}")

    print()
    print(f"{len(lines)} lines used, {len(problems)} skipped")
    for problem in problems:
        print(" -", problem)


if __name__ == "__main__":
    main()

pen        51.75
ink       276.00
total     327.75

2 lines used, 2 skipped
 - line 2: could not convert string to float: 'eight'
 - line 5: expected 3 fields, got 2