如何从 python 中的数字和单词列表中提取特定项目？

Question

i have a huge list of data in the given format.i need to extract all the data with year 2000.i get this error invalid literal for int() with base 10:'year'

['title','country','year','val',]
['bm','china','1987','2200']
['bm','japan','2000','1600']
['bm','germany','2000','70']
#it doesnt seem to work 
new=[]
for i in list:
    if i[2]==2000:
       new.append(int(i))

Answer 1

You can try

new = [i for i in list[1:] if '2000' == i[2]]

'list' is a keyword in python. Its best practice to avoid using it in code.

Answer 2

The reason you are getting literal error, is because your code is trying to convert String 'Year' to int. Remove the 1st list ( headers ) from the conversion.

Answer 3

1st, you should NOT be naming your variable as list , because list is a built-in data type of Python. You should NOT name your variables and functions the same as the built-in types and functions. Use something else, ex. mylist .

2nd, it's probably not working because you are including the list ['title', 'country', 'year', 'val',] in the loop, and i[2] will be "year" and when your tried to cast "year" (a string) to an int, it raised the error.

One option is to skip the 1st list that looks like a header.

mylist = [
    ['title','country','year','val',],
    ['bm','china','1987','2200'],
    ['bm','japan','2000','1600'],
    ['bm','germany','2000','70']
]

new=[]
for i in mylist[1:]:
    year = int(i[2])
    if year==2000:
       new.append(i)
print(new)
# [['bm', 'japan', '2000', '1600'], ['bm', 'germany', '2000', '70']]

Another option if you don't know whether the i[2] will be a valid integer value, is to try to cast it and then just skip it if it fails:

mylist = [
    ['title','country','year','val',],
    ['bm','china','1987','2200'],
    ['bm','japan','2000','1600'],
    ['bm','germany','2000','70']
]

new=[]
for i in mylist:
    try:
        year = int(i[2])
    except ValueError:
        continue
    if year==2000:
        new.append(i)
print(new)
# [['bm', 'japan', '2000', '1600'], ['bm', 'germany', '2000', '70']]