Regular expression template using lookahead assertions in Python

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-1
down vote

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I built the following regular expression pattern using grouping and named groups after Landsat's new product identifier pattern. It looks like this (see also link to pythex.org):

(?P<prefix>L)(?P<sensor>[C|O|T|E|M])(?P<satellite>0[14578])(?P<delimiter>_)(?P<processing_correction_level>(L1(?:TP|GT|GS)))(?P=delimiter)(?P<path>[012][0-9][0-9])(?P<row>[01][0-9][0-9]|2[0-4][0-3])(?P=delimiter)(?P<acquisition_year>19|20dd)(?P<acquisition_month>0[1-9]|1[012])(?P<acquisition_day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P<processing_year>19|20dd)(?P<processing_month>0[1-9]|1[012])(?P<processing_day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P<collection>0[12])(?P=delimiter)(?P<category>RT|T[1|2])(?P=delimiter)(?P<band>B[0-9Q][01A]?).TIF

Given a directory that contains, say, the following file(names):

LC08_L1TP_184033_20170328_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20171128_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20171128_20181027_01_RT_B1.TIF

LC08_L1TP_184033_20171128_20181027_01_RT_B4.TIF

LC08_L1TP_184033_20173328_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20181028_20181027_01_RT_BQA.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_ANG.txt

LC08_L1TP_184033_20181028_20181028_01_RT_B10.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B11.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B1.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B2.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B3.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B4.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B5.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B6.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B7.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B8.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B9.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_BQA.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_MTL.txt

LC08_L1TP_184033_20181128_20181027_01_RT_B1.TIF

LC08_L1TP_184033_20181128_20181027_01_RT_BQA.TIF

and a slightly modified template, i.e. the following:

(?P<prefix>L)(?P<sensor>[C|O|T|E|M])(?P<satellite>0[14578])(?P<delimiter>_)(?P<processing_correction_level>(L1(?:TP|GT|GS)))(?P=delimiter)(?P<path>[012][0-9][0-9])(?P<row>[01][0-9][0-9]|2[0-4][0-3])(?P=delimiter)(?P<acquisition_year>19|20\d\d)(?P<acquisition_month>0[1-9]|1[012])(?P<acquisition_day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P<processing_year>19|20\d\d)(?P<processing_month>0[1-9]|1[012])(?P<processing_day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P<collection>0[12])(?P=delimiter)(?P<category>RT|T[1|2])(?P=delimiter)(?P<band>B{BAND}).TIF

the following Python function:

def retrieve_selected_bands(bands, scene):

    """

    Retrieve user requested bands from a Landsat scene



    Parameters

    ----------

    bands :

        User requested bands



    scene :

        Landsat scene directory



    Returns

    -------

        Returns list of filenames of user requested bands



    Example

    -------

        ...

    """

    requested_bands = 

    for band in bands:

        for filename in os.listdir(scene):

            template = regular_expression_variable.format(BAND=band)

            pattern = re.compile(template)

            if pattern.match(filename):

                requested_bands.append(glob.glob(filename)[0])

    print

    print('n'.join(map(str, requested_bands)))

will retrieve successfully what is asked for, i.e.:

retrieve_selected_bands(bands, '.')



LC08_L1TP_184033_20181028_20181028_01_RT_B4.TIF

LC08_L1TP_184033_20171128_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20170328_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20171128_20181027_01_RT_B4.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B5.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B10.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B11.TIF

LC08_L1TP_184033_20181128_20181027_01_RT_BQA.TIF

LC08_L1TP_184033_20181028_20181027_01_RT_BQA.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_BQA.TIF

I want to understand if and how the regular expression template can be improved, i.e. become shorter and thus more readable, by using for example lookahead assertions, like:

(?P<prefix>L)(?P<sensor>[C|O|T|E|M])(?P<satellite>0[14578])(P<delimiter>_)(?P<processing_correction_level>(L1(?:TP|GT|GS)))(?P=delimiter)(?P<path>[012][0-9][0-9])(?P<row>[01][0-9][0-9]|2[0-4][0-3])(?P=delimiter)(?P<year>19|20dd)(?P<month>0[1-9]|1[012])(?P<day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P=year)(?P=month)(?P=day)(?P=delimiter)(?P<collection>0[12])(?P=delimiter)(?P<category>RT|T[1|2])(?P=delimiter)(?P<band>B[0-9Q][01A]?).TIF

However, the latter version of the template fails to capture all "valid" strings. If I am not wrong, it fails on the (?=day) part.

How can the first template be improved? I.e., become shorter and still include all date patterns of valid Landsat product identifier strings?

edited 9 hours ago

asked 17 hours ago

Nikos Alexandris

1023

New contributor

Hey, welcome to Code Review! This question does not match what this site is about. Code Review is about improving existing, working code. Code Review is not the site to ask for help in fixing or changing what your code does. Once the code does what you want, we would love to help you do the same thing in a cleaner way! Please see our help center for more information.
– Graipher
16 hours ago

@Graipher, if I copy-paste the python code that uses the first pattern, which works fine, and ask again, the same question (which is: can I make this template shorter?--so as to save space, make it perhaps more readable, so improving), will you then accept this question as a valid one for Code Review?
– Nikos Alexandris
10 hours ago

If you only use the first one and show valid Python code that uses it (just wrap it in a function) and preferably add those test cases you mention, it would probably be on-topic.
– Graipher
10 hours ago

@Graipher I tried to improve the question. Is it valid for Code Review now?
– Nikos Alexandris
9 hours ago

add a comment |

up vote
-1
down vote

favorite

I built the following regular expression pattern using grouping and named groups after Landsat's new product identifier pattern. It looks like this (see also link to pythex.org):

(?P<prefix>L)(?P<sensor>[C|O|T|E|M])(?P<satellite>0[14578])(?P<delimiter>_)(?P<processing_correction_level>(L1(?:TP|GT|GS)))(?P=delimiter)(?P<path>[012][0-9][0-9])(?P<row>[01][0-9][0-9]|2[0-4][0-3])(?P=delimiter)(?P<acquisition_year>19|20dd)(?P<acquisition_month>0[1-9]|1[012])(?P<acquisition_day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P<processing_year>19|20dd)(?P<processing_month>0[1-9]|1[012])(?P<processing_day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P<collection>0[12])(?P=delimiter)(?P<category>RT|T[1|2])(?P=delimiter)(?P<band>B[0-9Q][01A]?).TIF

Given a directory that contains, say, the following file(names):

LC08_L1TP_184033_20170328_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20171128_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20171128_20181027_01_RT_B1.TIF

LC08_L1TP_184033_20171128_20181027_01_RT_B4.TIF

LC08_L1TP_184033_20173328_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20181028_20181027_01_RT_BQA.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_ANG.txt

LC08_L1TP_184033_20181028_20181028_01_RT_B10.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B11.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B1.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B2.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B3.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B4.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B5.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B6.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B7.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B8.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B9.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_BQA.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_MTL.txt

LC08_L1TP_184033_20181128_20181027_01_RT_B1.TIF

LC08_L1TP_184033_20181128_20181027_01_RT_BQA.TIF

and a slightly modified template, i.e. the following:

(?P<prefix>L)(?P<sensor>[C|O|T|E|M])(?P<satellite>0[14578])(?P<delimiter>_)(?P<processing_correction_level>(L1(?:TP|GT|GS)))(?P=delimiter)(?P<path>[012][0-9][0-9])(?P<row>[01][0-9][0-9]|2[0-4][0-3])(?P=delimiter)(?P<acquisition_year>19|20\d\d)(?P<acquisition_month>0[1-9]|1[012])(?P<acquisition_day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P<processing_year>19|20\d\d)(?P<processing_month>0[1-9]|1[012])(?P<processing_day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P<collection>0[12])(?P=delimiter)(?P<category>RT|T[1|2])(?P=delimiter)(?P<band>B{BAND}).TIF

the following Python function:

def retrieve_selected_bands(bands, scene):

    """

    Retrieve user requested bands from a Landsat scene



    Parameters

    ----------

    bands :

        User requested bands



    scene :

        Landsat scene directory



    Returns

    -------

        Returns list of filenames of user requested bands



    Example

    -------

        ...

    """

    requested_bands = 

    for band in bands:

        for filename in os.listdir(scene):

            template = regular_expression_variable.format(BAND=band)

            pattern = re.compile(template)

            if pattern.match(filename):

                requested_bands.append(glob.glob(filename)[0])

    print

    print('n'.join(map(str, requested_bands)))

will retrieve successfully what is asked for, i.e.:

retrieve_selected_bands(bands, '.')



LC08_L1TP_184033_20181028_20181028_01_RT_B4.TIF

LC08_L1TP_184033_20171128_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20170328_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20171128_20181027_01_RT_B4.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B5.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B10.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B11.TIF

LC08_L1TP_184033_20181128_20181027_01_RT_BQA.TIF

LC08_L1TP_184033_20181028_20181027_01_RT_BQA.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_BQA.TIF

I want to understand if and how the regular expression template can be improved, i.e. become shorter and thus more readable, by using for example lookahead assertions, like:

(?P<prefix>L)(?P<sensor>[C|O|T|E|M])(?P<satellite>0[14578])(P<delimiter>_)(?P<processing_correction_level>(L1(?:TP|GT|GS)))(?P=delimiter)(?P<path>[012][0-9][0-9])(?P<row>[01][0-9][0-9]|2[0-4][0-3])(?P=delimiter)(?P<year>19|20dd)(?P<month>0[1-9]|1[012])(?P<day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P=year)(?P=month)(?P=day)(?P=delimiter)(?P<collection>0[12])(?P=delimiter)(?P<category>RT|T[1|2])(?P=delimiter)(?P<band>B[0-9Q][01A]?).TIF

However, the latter version of the template fails to capture all "valid" strings. If I am not wrong, it fails on the (?=day) part.

How can the first template be improved? I.e., become shorter and still include all date patterns of valid Landsat product identifier strings?

edited 9 hours ago

asked 17 hours ago

Nikos Alexandris

1023

New contributor

Hey, welcome to Code Review! This question does not match what this site is about. Code Review is about improving existing, working code. Code Review is not the site to ask for help in fixing or changing what your code does. Once the code does what you want, we would love to help you do the same thing in a cleaner way! Please see our help center for more information.
– Graipher
16 hours ago

@Graipher, if I copy-paste the python code that uses the first pattern, which works fine, and ask again, the same question (which is: can I make this template shorter?--so as to save space, make it perhaps more readable, so improving), will you then accept this question as a valid one for Code Review?
– Nikos Alexandris
10 hours ago

If you only use the first one and show valid Python code that uses it (just wrap it in a function) and preferably add those test cases you mention, it would probably be on-topic.
– Graipher
10 hours ago

@Graipher I tried to improve the question. Is it valid for Code Review now?
– Nikos Alexandris
9 hours ago

add a comment |

up vote
-1
down vote

favorite

I built the following regular expression pattern using grouping and named groups after Landsat's new product identifier pattern. It looks like this (see also link to pythex.org):

(?P<prefix>L)(?P<sensor>[C|O|T|E|M])(?P<satellite>0[14578])(?P<delimiter>_)(?P<processing_correction_level>(L1(?:TP|GT|GS)))(?P=delimiter)(?P<path>[012][0-9][0-9])(?P<row>[01][0-9][0-9]|2[0-4][0-3])(?P=delimiter)(?P<acquisition_year>19|20dd)(?P<acquisition_month>0[1-9]|1[012])(?P<acquisition_day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P<processing_year>19|20dd)(?P<processing_month>0[1-9]|1[012])(?P<processing_day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P<collection>0[12])(?P=delimiter)(?P<category>RT|T[1|2])(?P=delimiter)(?P<band>B[0-9Q][01A]?).TIF

Given a directory that contains, say, the following file(names):

LC08_L1TP_184033_20170328_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20171128_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20171128_20181027_01_RT_B1.TIF

LC08_L1TP_184033_20171128_20181027_01_RT_B4.TIF

LC08_L1TP_184033_20173328_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20181028_20181027_01_RT_BQA.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_ANG.txt

LC08_L1TP_184033_20181028_20181028_01_RT_B10.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B11.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B1.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B2.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B3.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B4.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B5.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B6.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B7.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B8.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B9.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_BQA.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_MTL.txt

LC08_L1TP_184033_20181128_20181027_01_RT_B1.TIF

LC08_L1TP_184033_20181128_20181027_01_RT_BQA.TIF

and a slightly modified template, i.e. the following:

(?P<prefix>L)(?P<sensor>[C|O|T|E|M])(?P<satellite>0[14578])(?P<delimiter>_)(?P<processing_correction_level>(L1(?:TP|GT|GS)))(?P=delimiter)(?P<path>[012][0-9][0-9])(?P<row>[01][0-9][0-9]|2[0-4][0-3])(?P=delimiter)(?P<acquisition_year>19|20\d\d)(?P<acquisition_month>0[1-9]|1[012])(?P<acquisition_day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P<processing_year>19|20\d\d)(?P<processing_month>0[1-9]|1[012])(?P<processing_day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P<collection>0[12])(?P=delimiter)(?P<category>RT|T[1|2])(?P=delimiter)(?P<band>B{BAND}).TIF

the following Python function:

def retrieve_selected_bands(bands, scene):

    """

    Retrieve user requested bands from a Landsat scene



    Parameters

    ----------

    bands :

        User requested bands



    scene :

        Landsat scene directory



    Returns

    -------

        Returns list of filenames of user requested bands



    Example

    -------

        ...

    """

    requested_bands = 

    for band in bands:

        for filename in os.listdir(scene):

            template = regular_expression_variable.format(BAND=band)

            pattern = re.compile(template)

            if pattern.match(filename):

                requested_bands.append(glob.glob(filename)[0])

    print

    print('n'.join(map(str, requested_bands)))

will retrieve successfully what is asked for, i.e.:

retrieve_selected_bands(bands, '.')



LC08_L1TP_184033_20181028_20181028_01_RT_B4.TIF

LC08_L1TP_184033_20171128_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20170328_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20171128_20181027_01_RT_B4.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B5.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B10.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B11.TIF

LC08_L1TP_184033_20181128_20181027_01_RT_BQA.TIF

LC08_L1TP_184033_20181028_20181027_01_RT_BQA.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_BQA.TIF

I want to understand if and how the regular expression template can be improved, i.e. become shorter and thus more readable, by using for example lookahead assertions, like:

(?P<prefix>L)(?P<sensor>[C|O|T|E|M])(?P<satellite>0[14578])(P<delimiter>_)(?P<processing_correction_level>(L1(?:TP|GT|GS)))(?P=delimiter)(?P<path>[012][0-9][0-9])(?P<row>[01][0-9][0-9]|2[0-4][0-3])(?P=delimiter)(?P<year>19|20dd)(?P<month>0[1-9]|1[012])(?P<day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P=year)(?P=month)(?P=day)(?P=delimiter)(?P<collection>0[12])(?P=delimiter)(?P<category>RT|T[1|2])(?P=delimiter)(?P<band>B[0-9Q][01A]?).TIF

However, the latter version of the template fails to capture all "valid" strings. If I am not wrong, it fails on the (?=day) part.

How can the first template be improved? I.e., become shorter and still include all date patterns of valid Landsat product identifier strings?

edited 9 hours ago

asked 17 hours ago

Nikos Alexandris

1023

New contributor

I built the following regular expression pattern using grouping and named groups after Landsat's new product identifier pattern. It looks like this (see also link to pythex.org):

(?P<prefix>L)(?P<sensor>[C|O|T|E|M])(?P<satellite>0[14578])(?P<delimiter>_)(?P<processing_correction_level>(L1(?:TP|GT|GS)))(?P=delimiter)(?P<path>[012][0-9][0-9])(?P<row>[01][0-9][0-9]|2[0-4][0-3])(?P=delimiter)(?P<acquisition_year>19|20dd)(?P<acquisition_month>0[1-9]|1[012])(?P<acquisition_day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P<processing_year>19|20dd)(?P<processing_month>0[1-9]|1[012])(?P<processing_day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P<collection>0[12])(?P=delimiter)(?P<category>RT|T[1|2])(?P=delimiter)(?P<band>B[0-9Q][01A]?).TIF

Given a directory that contains, say, the following file(names):

LC08_L1TP_184033_20170328_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20171128_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20171128_20181027_01_RT_B1.TIF

LC08_L1TP_184033_20171128_20181027_01_RT_B4.TIF

LC08_L1TP_184033_20173328_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20181028_20181027_01_RT_BQA.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_ANG.txt

LC08_L1TP_184033_20181028_20181028_01_RT_B10.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B11.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B1.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B2.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B3.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B4.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B5.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B6.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B7.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B8.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B9.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_BQA.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_MTL.txt

LC08_L1TP_184033_20181128_20181027_01_RT_B1.TIF

LC08_L1TP_184033_20181128_20181027_01_RT_BQA.TIF

and a slightly modified template, i.e. the following:

(?P<prefix>L)(?P<sensor>[C|O|T|E|M])(?P<satellite>0[14578])(?P<delimiter>_)(?P<processing_correction_level>(L1(?:TP|GT|GS)))(?P=delimiter)(?P<path>[012][0-9][0-9])(?P<row>[01][0-9][0-9]|2[0-4][0-3])(?P=delimiter)(?P<acquisition_year>19|20\d\d)(?P<acquisition_month>0[1-9]|1[012])(?P<acquisition_day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P<processing_year>19|20\d\d)(?P<processing_month>0[1-9]|1[012])(?P<processing_day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P<collection>0[12])(?P=delimiter)(?P<category>RT|T[1|2])(?P=delimiter)(?P<band>B{BAND}).TIF

the following Python function:

def retrieve_selected_bands(bands, scene):

    """

    Retrieve user requested bands from a Landsat scene



    Parameters

    ----------

    bands :

        User requested bands



    scene :

        Landsat scene directory



    Returns

    -------

        Returns list of filenames of user requested bands



    Example

    -------

        ...

    """

    requested_bands = 

    for band in bands:

        for filename in os.listdir(scene):

            template = regular_expression_variable.format(BAND=band)

            pattern = re.compile(template)

            if pattern.match(filename):

                requested_bands.append(glob.glob(filename)[0])

    print

    print('n'.join(map(str, requested_bands)))

will retrieve successfully what is asked for, i.e.:

retrieve_selected_bands(bands, '.')



LC08_L1TP_184033_20181028_20181028_01_RT_B4.TIF

LC08_L1TP_184033_20171128_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20170328_20161027_01_RT_B4.TIF

LC08_L1TP_184033_20171128_20181027_01_RT_B4.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B5.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B10.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_B11.TIF

LC08_L1TP_184033_20181128_20181027_01_RT_BQA.TIF

LC08_L1TP_184033_20181028_20181027_01_RT_BQA.TIF

LC08_L1TP_184033_20181028_20181028_01_RT_BQA.TIF

I want to understand if and how the regular expression template can be improved, i.e. become shorter and thus more readable, by using for example lookahead assertions, like:

(?P<prefix>L)(?P<sensor>[C|O|T|E|M])(?P<satellite>0[14578])(P<delimiter>_)(?P<processing_correction_level>(L1(?:TP|GT|GS)))(?P=delimiter)(?P<path>[012][0-9][0-9])(?P<row>[01][0-9][0-9]|2[0-4][0-3])(?P=delimiter)(?P<year>19|20dd)(?P<month>0[1-9]|1[012])(?P<day>0[1-9]|[12][0-9]|3[01])(?P=delimiter)(?P=year)(?P=month)(?P=day)(?P=delimiter)(?P<collection>0[12])(?P=delimiter)(?P<category>RT|T[1|2])(?P=delimiter)(?P<band>B[0-9Q][01A]?).TIF

However, the latter version of the template fails to capture all "valid" strings. If I am not wrong, it fails on the (?=day) part.

How can the first template be improved? I.e., become shorter and still include all date patterns of valid Landsat product identifier strings?

python regex template

edited 9 hours ago

asked 17 hours ago

Nikos Alexandris

1023

New contributor

edited 9 hours ago

asked 17 hours ago

Nikos Alexandris

1023

New contributor

edited 9 hours ago

asked 17 hours ago

Nikos Alexandris

1023

New contributor

asked 17 hours ago

Nikos Alexandris

1023

asked 17 hours ago

Nikos Alexandris

1023

New contributor

Nikos Alexandris is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

Hey, welcome to Code Review! This question does not match what this site is about. Code Review is about improving existing, working code. Code Review is not the site to ask for help in fixing or changing what your code does. Once the code does what you want, we would love to help you do the same thing in a cleaner way! Please see our help center for more information.
– Graipher
16 hours ago

@Graipher, if I copy-paste the python code that uses the first pattern, which works fine, and ask again, the same question (which is: can I make this template shorter?--so as to save space, make it perhaps more readable, so improving), will you then accept this question as a valid one for Code Review?
– Nikos Alexandris
10 hours ago

If you only use the first one and show valid Python code that uses it (just wrap it in a function) and preferably add those test cases you mention, it would probably be on-topic.
– Graipher
10 hours ago

@Graipher I tried to improve the question. Is it valid for Code Review now?
– Nikos Alexandris
9 hours ago

add a comment |

Hey, welcome to Code Review! This question does not match what this site is about. Code Review is about improving existing, working code. Code Review is not the site to ask for help in fixing or changing what your code does. Once the code does what you want, we would love to help you do the same thing in a cleaner way! Please see our help center for more information.
– Graipher
16 hours ago

@Graipher, if I copy-paste the python code that uses the first pattern, which works fine, and ask again, the same question (which is: can I make this template shorter?--so as to save space, make it perhaps more readable, so improving), will you then accept this question as a valid one for Code Review?
– Nikos Alexandris
10 hours ago

If you only use the first one and show valid Python code that uses it (just wrap it in a function) and preferably add those test cases you mention, it would probably be on-topic.
– Graipher
10 hours ago

@Graipher I tried to improve the question. Is it valid for Code Review now?
– Nikos Alexandris
9 hours ago

Hey, welcome to Code Review! This question does not match what this site is about. Code Review is about improving existing, working code. Code Review is not the site to ask for help in fixing or changing what your code does. Once the code does what you want, we would love to help you do the same thing in a cleaner way! Please see our help center for more information.
– Graipher
16 hours ago

@Graipher, if I copy-paste the python code that uses the first pattern, which works fine, and ask again, the same question (which is: can I make this template shorter?--so as to save space, make it perhaps more readable, so improving), will you then accept this question as a valid one for Code Review?
– Nikos Alexandris
10 hours ago

If you only use the first one and show valid Python code that uses it (just wrap it in a function) and preferably add those test cases you mention, it would probably be on-topic.
– Graipher
10 hours ago

@Graipher I tried to improve the question. Is it valid for Code Review now?
– Nikos Alexandris
9 hours ago

add a comment |

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