Python，从Excel列中提取数字并写为输出

Question

Trying to extract the number from columns in an Excel file, and write them into the next columns.

Matching criteria: any number of length five, either started with “PB” or not

I've limited the length of the number match to five however there are a “16” extracted (row#2, column D)

How I can improve it? Thank you.

import xlwt, xlrd, re
from xlutils.copy import copy 

workbook = xlrd.open_workbook("C:\\Documents\\num.xlsx")
old_sheet = workbook.sheet_by_name("Sheet1")

wb = copy(workbook) 
sheet = wb.get_sheet(0)

number_of_ships = old_sheet.nrows

for row_index in range(0, old_sheet.nrows):

    Column_a = old_sheet.cell(row_index, 0).value   
    Column_b = old_sheet.cell(row_index, 1).value

    a_b = Column_a + Column_b

    found_PB = re.findall(r"[PB]+(\d{5})", a_b, re.I)
    list_of_numbers = re.findall(r'\d+', a_b)

    for f in found_PB:
        if len(f) == 5:
            sheet.write(row_index, 2, "";"".join(found_PB))

    for l in list_of_numbers:
        if len(l) == 5:
            sheet.write(row_index, 3, "";"".join(list_of_numbers))

wb.save("C:\\Documents\\num-1.xls")    

Answer 1

Your \\d+ pattern matches any 1 or more digits, thus the 16 value is matched. Your [PB]+ character class matches either P or B one or more times, so it restricts the digits to be preceded with either P or B . As you want to match any digits, you actually do not need that restriction (if an A can be preceded with something optionally , the restriction no longer makes sense).

You also seem to need to extract 5 digit string exactly, when no other digits precedes or follows them. You may do that with (?<!\\d)\\d{5}(?!\\d) . The (?<!\\d) negative lookbehind makes sure there is no digit immediately to the left of the current location, \\d{5} consumes 5 digits, and the (?!\\d) negative lookahead makes sure there is no digit immediately to the right of the current location. That makes the if len(l) == 5: line redundant and you may omit the whole part of code related to list_of_numbers .

So, you may just use

import xlwt, xlrd, re
from xlutils.copy import copy 

workbook = xlrd.open_workbook("C:\\Documents\\num.xlsx")
old_sheet = workbook.sheet_by_name("Sheet1")

wb = copy(workbook) 
sheet = wb.get_sheet(0)

number_of_ships = old_sheet.nrows

for row_index in range(0, old_sheet.nrows):

    Column_a = old_sheet.cell(row_index, 0).value   
    Column_b = old_sheet.cell(row_index, 1).value

    a_b = Column_a + Column_b

    found_PB = re.findall(r"(?<!\d)\d{5}(?!\d)", a_b)

    for f in found_PB:
            sheet.write(row_index, 2, "";"".join(found_PB))

wb.save("C:\\Documents\\num-1.xls")    

Answer 2

You may use this: ^(?:PB)?\\d{5}$

Demo

Explained:

^           # Begin of line/string
  (?:       # Begin of group
     PB     #   Literal 'PB'
  )         # End of group
  ?         # Make the previous group optional (? means 0 or 1 times)
  \d{5}     # 5 digits
$           # End of line/string

It is important to use the $ , since if you just wrote ^(?:PB)?\\d{5} you would match 6 digit numbers even if you wrote \\d{5} this is because you would match the first five digits and you would stop there, without knowing if there are more digits.

If your data may start or end with spaces you may use this instead: ^\\s*(?:PB)?\\d{5}\\s*$ It basically adds \\s* at the beginning and the end of the regex. \\s* means 0 or more spaces.