搜索文本文件中的字符串，保存包含列表中某项的行，如果文本文件中不存在该项，则返回NA

Question

I have a list of items

ls=["John","Tanner",'Mary','Anna','25'] 

and a text file:

 V1 'John' 'blablablabla...'
 V2 'Anna' 'blablablabla...'
 V3 'Josh' 'blablablabla...'
 V4 'Mary' 'blablablabla...'
 V5 'Steven' 'blablablabla...'

I want to search each item of the list inside the text file, and save the line that contains the item.

var=[]
with open('C:/Maryam/example/test.txt', 'r') as file:
    for line in file:
        for item in ls:
            if item in line:
                var.append(line)

var   

The output already looks like:

["  V1 'John' 'blablablabla...'\n","  V2 'Anna' 'blablablabla...'\n",
"  V4 'Mary' 'blablablabla...'\n"]

But I expect to get something like this:

["  V1 'John' 'blablablabla...'\n", 'NA' , "  V2 'Anna' 'blablablabla...'\n",
"  V4 'Mary' 'blablablabla...'\n", 'NA']

I tried to generate 'NA' in the list but couldn't figure it out. The reason I used for line in file: cause I want to save the whole line including specific string. Is there any way to use regular expressions, so I could get rid of the for loop on the lines and then save the whole line. Thank you.

Answer 1

You could change your code to check if anything was found on each different line:

var=[]
with open('C:/Maryam/example/test.txt', 'r') as file:
    for line in file:
        was_found=False
        for item in var:
            if item in line:
                var.append(line)
                was_found=True
        if not was_found:
            var.append("NA")

Answer 2

I will suggest to use a dictionary instead of a list so you can store an entry for each element to search and the corresponding line (if any, NA otherwise):

# Initialize the result dictionary
result = {}
for name in ls:
    result[name] = 'NA'

# Process the file
with open('C:/Maryam/example/test.txt', 'r') as file:
    for line in file:
        # For each line check if it contains a reserved keyword
        for name in result.keys():
            if name in line:
                result[name] = line

# Show result (key = name, value = line content)
result

# Show only the values (line contents)
result.values()

Answer 3

The 'for-break-else' construction can be used,too:

for item in ls:
    if item in line:
        var.append(line)
        break
else:
        var.append("NA")