找到字符串的哪个部分与正则表达式python不匹配

Question

In order to see if a filename is correctly named (using re) I use the following regular expression pattern :

*^S_hc_[0-9]{1,2}\.[0-9]{1,2}\.[0-9]{1,2}_[0-9]{4,4}-[0-9]{1,3}T[0-9]{6,6}\.xml$"*

Here is a correct file name : *S_hc_1.2.3_2014-213T123121.xml*

Here is an incorrect file name : *S_hc_1.2.IncorrectName_2014-213T123121.xml*

I would like to know if a simple way to retrieve the part of the file which to do not match exits.

In the end, an error message would display :

Error, incorrect file name, the part 'IncorrectName' does not match with expected name. 

Answer 1

You can use re.split and a generator expression within next but you also need to check the structure of your string that match waht you want, you can do it with following re.match :

re.match(r"^S_hc_(.*)\.(.*)\.(.*)_(.*)-(.*)\.xml$",s2)

And in code:

>>> import re
>>> s2 ='S_hc_1.2.IncorrectName_2014-213T123121.xml'
>>> s1
'S_hc_1.2.3_2014-213T123121.xml'
#with s1
>>> next((i for i in re.split(r'^S_hc_|[0-9]{1,2}\.|[0-9]{1,2}_|_|[0-9]{4,4}|-|[0-9]{1,3}T[0-9]{6}|\.|xml$',s1) if i and re.match(r"^S_hc_(.*)\.(.*)\.(.*)_(.*)-(.*)\.xml$",s2)),None)
#with s2
>>> next((i for i in re.split(r'^S_hc_|[0-9]{1,2}\.|[0-9]{1,2}_|_|[0-9]{4,4}|-|[0-9]{1,3}T[0-9]{6}|\.|xml$',s2) if i and re.match(r"^S_hc_(.*)\.(.*)\.(.*)_(.*)-(.*)\.xml$",s2)),None)
'IncorrectName'

All you need is to use pip ( | ) between unique part of your regex patterns,then the split function will split your string based on one of that patterns.

And the part that doesn't match with one of your pattern will not be split and you can find it with looping over your split text!

next(iterator[, default])

Retrieve the next item from the iterator by calling its next() method. If default is given, it is returned if the iterator is exhausted, otherwise StopIteration is raised.

If you want in several line :

>>> for i in re.split(r'^S_hc_|[0-9]{1,2}\.|[0-9]{1,2}_|_|[0-9]{4,4}|-|[0-9]{1,3}T[0-9]{6}|\.|xml$',s2):
...   if i and re.match(r"^S_hc_(.*)\.(.*)\.(.*)_(.*)-(.*)\.xml$",s2):
...        print i
... 
IncorrectName

Answer 2

Maybe this is a longer solution but it will tell you what failed and what it expected. It is similar to Kasra's solution - breaking up the file name into individual bits and matching them in turn. This allows you to find out where the matching breaks:

import re
# break up the big file name pattern into individual bits that we can match
RX      = re.compile
pattern = [
        RX(r"\*"),
        RX(r"S_hc_"),
        RX(r"[0-9]{1,2}"),
        RX(r"\."),
        RX(r"[0-9]{1,2}"),
        RX(r"\."),
        RX(r"[0-9]{1,2}"),
        RX(r"_"),
        RX(r"[0-9]{4}"),
        RX(r"-"),
        RX(r"[0-9]{1,3}"),
        RX(r"T"),
        RX(r"[0-9]{6}"),
        RX(r"\.xml"),
        RX(r"\*")
        ]

# 'fn' is the file name matched so far
def reductor(fn, rx):
    if fn is None:
        return None
    mo = rx.match(fn)
    if mo is None:
        print "File name mismatch: got {}, expected {}".format(fn, rx.pattern)
        return None
    # proceed with the remainder of the string
    return fn[mo.end():]


validFile = lambda fn: reduce(reductor, pattern, fn) is not None

Let's test it:

print validFile("*S_hc_1.2.3_2014-213T123121.xml*")
print validFile("*S_hc_1.2.IncorrectName_2014-213T123121.xml*")

Outputs:

True
File name mismatch: got IncorrectName_2014-213T123121.xml*, expected [0-9]{1,2}
False

Answer 3

Here is the method I am going to use, please let me know if cases mismatch:

def verifyFileName(self, filename__, pattern__):
    '''
    Verifies if a file name is correct
    :param filename__: file name 
    :param pattern__: pattern
    :return: empty string if file name is correct, otherwise the incorrect part of file
    '''
    incorrectPart =""
    pattern = pattern__.replace('\.','|\.|').replace('_','|_|')
    for i in re.split(pattern, filename__):
        if len(i)>1:
            incorrectPart = i
    return incorrectPart

Answer 4

Here's the counterexample. I've taken your method and defined three test cases - file names plus expected output.

Here's the output, the code follows below:

$> python m.py
S_hc_1.2.3_2014-213T123121.xml: PASS [expect None got None]
S_hc_1.2.3_Incorrect-213T123121.xml: PASS [expect Incorrect- got Incorrect-]
X_hc_1.2.3_2014-213T123121.xml: FAIL [expect X got None]

This is the code - cut & paste & run it.

def verifyFileName(filename__, pattern__):
    '''
    Verifies if a file name is correct
    :param filename__: file name 
    :param pattern__: pattern
    :return: empty string if file name is correct, otherwise the incorrect part of file
    '''
    incorrectPart = None
    pattern = pattern__.replace('\.','|\.|').replace('_','|_|')
    for i in re.split(pattern, filename__):
        if len(i)>1:
            incorrectPart = i
    return incorrectPart


pattern = "^S_hc_[0-9]{1,2}\.[0-9]{1,2}\.[0-9]{1,2}_[0-9]{4,4}-[0-9]{1,3}T[0-9]{6,6}\.xml$"

# list of test cases: filenames + expected return from verifyFileName:
testcases = [
        # correct file name
        ("S_hc_1.2.3_2014-213T123121.xml", None),
        # obviously incorrect
        ("S_hc_1.2.3_Incorrect-213T123121.xml", "Incorrect-"),
        # subtly incorrect but still incorrect
        ("X_hc_1.2.3_2014-213T123121.xml", "X")
        ]

for (fn, expect) in testcases:
    res = verifyFileName(fn, pat)
    print "{}: {} [expect {} got {}]".format(fn, "PASS" if res==expect else "FAIL", expect, str(res))