Python中'if x in else'语句在Jupyter Notebook中失效问题排查

错误根源 #

你的if条件逻辑写法有误。Python中"sunny" or "lovely" in sitrep的执行顺序是先判断"sunny"的布尔值——非空字符串在布尔语境下永远为True，所以整个条件表达式直接返回True，完全不会去检查"lovely" in sitrep这部分。这就导致不管目标字符串里有没有指定关键词，代码都会执行if块的内容。

修正方案 #

有两种简洁的正确写法：

写法1：分别判断每个关键词 #

明确对每个关键词做in判断，再用or连接：

sitrep = "it is horrible weather"
print("The sitrep is: " + sitrep)
print(type(sitrep))
if "sunny" in sitrep or "lovely" in sitrep:
    print("sunny or lovely have been detected")
else:
    print("neither has been detected")

写法2：用any()函数（适合关键词较多的场景） #

把关键词放到列表里，用生成器表达式配合any()判断：

sitrep = "it is horrible weather"
target_words = ["sunny", "lovely"]
print("The sitrep is: " + sitrep)
print(type(sitrep))
if any(word in sitrep for word in target_words):
    print("sunny or lovely have been detected")
else:
    print("neither has been detected")

验证结果 #

修正后的代码运行后，会输出预期结果：

it is horrible weather
<class 'str'>
neither has been detected

内容的提问来源于stack exchange，提问作者e-driver1