检查一个列表中的项是否存在于另一个列表中

Question

I have the following data. My goal is to check whether each row is part of the US or not.

data = [', Accomack, Virginia, USA',
 'Elkin, Surry, North Carolina, USA',
 'Philippines',
 '(null)',
 'Texas, United States',
 'Kingston, Washington, Rhode Island, United States']

I first used the following to split them into lists within the list and remove the white space:

place = []

for d in data:

   row = d.split(',')

   rowlist = []

   for r in row:

      r_stripped = r.strip()

      rowlist.append(r_stripped)

   place.append(rowlist)

place

I got the following output, which is what I expected:

[['', 'Accomack', 'Virginia', 'USA'],
 ['Elkin', 'Surry', 'North Carolina', 'USA'],
 ['Philippines'],
 ['(null)'],
 ['Texas', 'United States'],
 ['Kingston', 'Washington', 'Rhode Island', 'United States']]

Then I used the following to try to see if each item is in the US or not:

country = []

US = ['USA', 'United States'] 

for p in place:
    for item in US:
        if item in p:
            c = 'US'

        else:
            c = 'Non-US'
    country.append(c)

country

For some reason, the code is not able to capture the first two rows as part of US.

['Non-US', 'Non-US', 'Non-US', 'Non-US', 'US', 'US']

It's even more curious if i remove the 'else: c = 'Non-US' condition, everything becomes 'US'.

Can anyone please tell me what I am not doing right? Thanks!

Answer 1

You should check if any item in p is in the list named US by updating the inner loop like below:

>>> for p in place:
...     for item in p:
...         if item in US:
...             c = "US"
...             break
...     else:
...         c = "Non-US"
...     country.append(c)

The else clause of the inner for loop is executed only if loop doesn't break . When you see item in the US list, you break out of the loop for the next p in the line.

--

However, you can make it more user-readable by leveraging any() and a little bit of list comprehensions :

>>> ["US" if any(item in US for item in p) else "Non-US" for p in place]
['US', 'US', 'Non-US', 'Non-US', 'US', 'US']

--

any() also helps you eliminate the inner loop totally:

>>> for p in place:
...     if any(item in US for item in p):
...         c = "US"
...     else:
...         c = "Non-US"
...     country.append(c)

Answer 2

new_data = filter(lambda x: 'USA' in x or 'United States' in x, data)
return new_data