how to delete all lines containing Letters and characters for a textfile-CodePudding

I have a textfile containing words, numbers, and characters. I want to delete all lines with the characters and words, and keep the lines with numbers. I found out that all those lines with words and characters have the letter of "r". so I wrote my code as:

The textfile contains these lines as an example:

-- for example
-- 7 Febraury 2022
5 7 1 5 3.0 2
3*2 3 5 7.0 3

and I want to keep these 2 lines:

5 7 1 5 3.0 2
3*2 3 5 7.0 3

This is the code written: textfile = open('test.txt', 'r') A = textfile.readlines()

L = []
for index,name in enumerate(A):
    if 'r' in name:
        L.append(index)

for idx in sorted(L, reverse = True):
    del A[idx]

I know it is not a good way to do that, is there any suggestion to do that?

CodePudding user response：

you can find only the words using regex

import re
with open(r'text_file.txt', 'r') as f:
    data = f.readlines()

with open(r'text_file.txt', 'w') as f:
    for line in data:
        if re.findall(r"(?!^\d $)^. $", line):
            f.write(line)

CodePudding user response：

If you want to do this without importing anything (e.g., re) then you could do this:

keep_these = []

def is_valid(t):
    try:
        float(t.replace('*', '0'))
        return True
    except ValueError:
        pass
    return False

with open('test.txt', encoding='utf-8') as infile:
    for line in infile:
        if all(is_valid(t) for t in line.strip().split()):
            keep_these.append(line)

print(keep_these)

Thus the keep_these list will contain references to the lines you want to keep which you could, for example, use to re-write the file

CodePudding user response：

You can use the regex library re. One way to do that is to loop through the lines and then keep the line only if re.match("[^0-9 ]", line) == None.