如何将其转化为Python列表理解？

Question

我想提高效率,但我无法弄清楚如何将其转化为python列表理解.

coupons = []
for source in sources:
    for coupon in source:
        if coupon.code_used not in coupons:
            coupons.append(coupon.code_used)

Answer 1

您无法访问当前创建的列表,但如果订单不重要,您可以使用set:

coupons = set(coupon.code_used for source in sources for coupon in source)