I came up with the below which finds a string in a row and copies that row to a new file. I want to replace Foo23 with something more dynamic (i.e. [0-9], etc.), but I cannot get this, or variables or regex, to work. It doesn't fail, but I also get no results. Help? Thanks.
with open('C:/path/to/file/input.csv') as f:
with open('C:/path/to/file/output.csv', "w") as f1:
for line in f:
if "Foo23" in line:
f1.write(line)
Based on your comment, you want to match lines whenever any three letters followed by two numbers are present, e.g. foo12 and bar54. Use regex!
import re
pattern = r'([a-zA-Z]{3}\d{2})\b'
for line in f:
if re.findall(pattern, line):
f1.write(line)
This will match lines like 'some line foo12' and 'another foo54 line', but not 'a third line foo' or 'something bar123'.
Breaking it down:
pattern = r'( # start capture group, not needed here, but nice if you want the actual match back
[a-zA-Z]{3} # any three letters in a row, any case
\d{2} # any two digits
) # end capture group
\b # any word break (white space or end of line)
'
If all you really need is to write all of the matches in the file to f1, you can use:
matches = re.findall(pattern, f.read()) # finds all matches in f
f1.write('\n'.join(matches)) # writes each match to a new line in f1
\w{3} will match much more than just 3 letters
my_string, it isn't being used
In essence, your question boils down to: "I want to determine whether the string matches pattern X, and if so, output it to the file". The best way to accomplish this is to use a reg-ex. In Python, the standard reg-ex library is re. So,
import re
matches = re.findall(r'([a-zA-Z]{3}\d{2})', line)
Combining this with file IO operations, we have:
data = []
with open('C:/path/to/file/input.csv', 'r') as f:
data = list(f)
data = [ x for x in data if re.findall(r'([a-zA-Z]{3}\d{2})\b', line) ]
with open('C:/path/to/file/output.csv', 'w') as f1:
for line in data:
f1.write(line)
Notice that I split up your file IO operations to reduce nesting. I also removed the filtering outside of your IO. In general, each portion of your code should do "one thing" for ease of testing and maintenance.
r"[A-Za-z][A-Za-z][A-Za-z]\d\d"...but I cannot get this, or variables or regex, to work.- please read minimal reproducible example. Show us what you are trying to do that doesn't work - include an example input string(s).r"[A-Za-z][A-Za-z][A-Za-z]\d\d"Tryimport reand then testif re.search(r"[A-Za-z][A-Za-z][A-Za-z]\d\d", line):or regexin my initial question, I meant that I did tryimport reetc. etc.