Michael Torrie wrote:
> On 11/02/2015 07:42 PM, Tim Chase wrote:
>> On 2015-11-02 20:09, Seymore4Head wrote:
>>> How do I make a regular expression that returns true if the end of
>>> the line is an asterisk
>>
>> Why use a regular expression?
>>
>> if line[-1] == '*':
>> yep(line)
>> else:
>> nope(line)
>
> Indeed, sometimes Jamie Zawinski's is often quite appropriate:
>
> Some people, when confronted with a problem, think "I know, I'll use
> regular expressions." Now they have two problems.
Incidentally the code example has two "problems", too.
- What about the empty string?
- What about lines with a trailing "\n", i. e. as they are usually delivered
when iterating over a file?
Below is a comparison of some of your options. The "one obvious way"
line.rstrip("\n").endswith("*") is not included ;)
$ cat starry_table.py
import re
def show_table(data, header):
rows = [header]
rows.extend([str(c) for c in row] for row in data)
widths = [max(len(row[i]) for row in rows) for i in range(len(header))]
template = " ".join("{:%d}" % w for w in widths)
for row in rows:
print(template.format(*row))
def compare(sample_lines):
for line in sample_lines:
got_re = bool(re.compile("\*$").search(line))
got_re_M = bool(re.compile("\*$", re.M).search(line))
got_endswith = line.endswith("*")
got_endswith2 = line.endswith(("*", "*\n"))
got_substring = line[-1:] == "*"
try:
got_char = line[-1] == "*"
except IndexError:
got_char = "#exception"
results = (
got_re, got_re_M,
got_endswith, got_endswith2,
got_substring, got_char)
yield (
["", "X"][len(set(results)) > 1],
repr(line)) + results
SAMPLE = ["", "\n", "foo\n", "*\n", "*", "foo*", "foo*\n", "foo*\nbar"]
HEADER = [
"", "line", "regex", "re.M",
"endswith", 'endswith(("*", "*\\n"))',
"substring", "char"]
if __name__ == "__main__":
show_table(compare(SAMPLE), HEADER)
$ python3 starry_table.py
line regex re.M endswith endswith(("*", "*\n")) substring char
X '' False False False False False
#exception
'\n' False False False False False
False
'foo\n' False False False False False
False
X '*\n' True True False True False
False
'*' True True True True True True
'foo*' True True True True True True
X 'foo*\n' True True False True False
False
X 'foo*\nbar' False True False False False
False
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