try and except

Code inside try: runs normally; if it raises an error, Python jumps to the matching except SomeError: block instead of stopping the program. Catch the specific error you expect: ZeroDivisionError for dividing by zero, ValueError for int("abc"), IndexError for a list position that does not exist, KeyError for a missing dictionary key. A bare except: hides real bugs.

Optional parts: else: runs when no error happened, finally: runs no matter what (closing files). Returning a sensible fallback, like None, from the except block is a common shape for helper functions.

def parse(text):
    try:
        return float(text)
    except ValueError:
        return None

print(parse("2.5"), parse("two"))   # 2.5 None

Your task

Write safe_divide(a, b) returning a / b or None when b is zero, read_int(text) returning the integer value of the text or None when it is not one, and first_item(items) returning the first item or None when the list is empty. Use try/except in each.

def safe_divide(a, b):
    try:
        return a / b
    except ZeroDivisionError:
        return None


def read_int(text):
    try:
        return int(text)
    except ValueError:
        return None


def first_item(items):
    try:
        return items[0]
    except IndexError:
        return None