Hey there! Let's break this down clearly since you're just starting out with Python.

First, let's understand what pytz.country_timezones[x] actually is: it's a list of strings, where each string is a full timezone name like 'Asia/Shanghai' or 'Asia/Tokyo'.

The Problem With Your First Code #

Your first snippet uses this condition:

if "Asia" in pytz.country_timezones[x]:

In Python, when you use in with a list, it checks if the exact string you're looking for is an element in that list. So here, you're asking: "Is the string 'Asia' directly present as an item in this list?"

But since all the elements in pytz.country_timezones[x] are longer strings (like 'Asia/Shanghai'), the exact string 'Asia' isn't in the list. That's why your condition never evaluates to True, and you get no output.

Why the Second Code Works #

Your second snippet fixes this by looping through each element in the list first:

for y in pytz.country_timezones[x]:
    if "Asia" in y:

Here, y represents each individual timezone string in the list (like 'Asia/Shanghai'). Now, when you use if "Asia" in y, you're checking if the substring 'Asia' exists inside that specific timezone string—not if 'Asia' is a standalone element in the list.

This makes sense because you want to find countries whose timezone lists include any timezone that starts with (or contains) "Asia", not countries that have a timezone literally named just "Asia".

A Quick Example to Illustrate #

Let's say pytz.country_timezones['CN'] returns:

['Asia/Shanghai', 'Asia/Urumqi']

• First code check: "Asia" in ['Asia/Shanghai', 'Asia/Urumqi'] → False (no element is exactly "Asia")
• Second code check: For y = 'Asia/Shanghai', "Asia" in y → True (the substring exists in the string)

Key Takeaway #

• Use in on a list to check if an exact item exists in that list.
• To check if any item in a list contains a substring, you need to loop through each item and check the substring against that item individually.

内容的提问来源于stack exchange，提问作者Saurabh Thakur