如何用Lambda与filter筛选非停产（discontinued=0）且单价>15的产品？

Hey there! Let's fix up that filter code and make it work properly. Your current attempt has a few syntax missteps—let's break down what went wrong, then show the correct approach.

What's Wrong with Your Current Code? #

Your line print(list(filter(lambda x: x=0,>15,products))) has two key issues:

1. Incorrect condition syntax: You can't separate multiple conditions with commas, and x=0 is an assignment (not a check for equality—use == instead).
2. Missing key access: You didn't specify that you're checking the discontinued and unit_price attributes/keys of each product (I'm assuming each product is a dictionary or object with these fields).

Correct filter() + Lambda Implementation #

Assuming each item in your products list is a dictionary (like {'discontinued': 0, 'unit_price': 22.5}), here's the fixed code:

# Filter to keep non-discontinued (discontinued=0) and unit_price >15.0
filtered_products = list(filter(lambda product: product['discontinued'] == 0 and product['unit_price'] > 15.0, products))
print(filtered_products)

Let's break this down:

• lambda product: ...: This anonymous function takes each product from the list as input.
• product['discontinued'] == 0: Checks if the product is not discontinued (note the double equals == for equality checks).
• product['unit_price'] > 15.0: Ensures the unit price is above 15.0.
• and: Ensures both conditions must be true for the product to be kept.
• list(...): Converts the filter object (an iterator) into a concrete list you can print or use elsewhere.

A More Pythonic Alternative: List Comprehension #

Many Python developers prefer list comprehensions over filter() + lambda because they're often more readable and easier to debug. Here's the same logic written this way:

filtered_products = [
    product for product in products 
    if product['discontinued'] == 0 and product['unit_price'] > 15.0
]
print(filtered_products)

This does exactly the same thing, but the syntax is more straightforward—you're explicitly saying "for each product in products, keep it if both conditions are met."

内容的提问来源于stack exchange，提问作者Chris Ged