当文件具有奇怪的格式时，对文本文件的行进行数字排序

Question

I'm having an issue comprehending how to do this. I have a txt file handling birthdays as such:

**January birthdays:**
**17** - !@Mark
**4** - !@Jan
**15** - !@Ralph

**February birthdays:**
**27** - !@Steve
**19** - !@Bill
**29** - !@Bob

The list continues for every month, each month is separated by a blank line. How on Earth do you sort the days sequentially with formatting like this?

For example January should be:

**January birthdays:**
**4** - !@Jan
**15** - !@Ralph 
**17** - !@Mark

What I've brainstormed:

I thought maybe I could potentially use readlines() from specific indexes and then save each line to a list, check the integer somehow, and then re-write the file properly. But this seems so tedious and frankly seems like the totally wrong idea.

I also considered using partial() to read until a stop condition such as the line of the next month and then sort somehow based on that.

Does Python offer any easier way to do something like this?

Answer 1

You can do it as follows.

Code

import re

def order_month(month_of_entries):
    '''
        Order lines for a Month of entries
    '''
    # Sort key based upon number in line
    # First line in Month does not have a number, 
    # so key function returns 0 for it so it stays first
    month_of_entries.sort(key=lambda x: int(p.group(0)) if (p:=re.search('\d+', x)) else 0)
            
# Process input file
with open('input.txt', 'r') as file:
    results = []
    months_data = []
    for line in file:
        line = line.rstrip()
        if line:
            months_data.append(line)
        else:
            # blank line
            # Order files for this month
            order_month(months_data)
            results.append(months_data)
            
            # Setup for next month
            months_data = []
    else:
        # Reached end of file
        # Order lines for last month
        if months_data:
            order_entries(months_data)
            results.append(months_data)
               
# Write to output file
with open('output.txt', 'w') as file:
    for i, months_data in enumerate(results):
        # Looping over each month
        for line in months_data:
            file.write(line + '\n')
        # Add blank line if not last month
        if i < len(results) - 1:
            file.write('\n')           
         

Output

**January birthdays:**
**4** - !@Jan
**15** - !@Ralph
**17** - !@Mark

**February birthdays:**
**19** - !@Bill
**27** - !@Steve
**29** - !@Bob

Alternativee, that also sort months if necessary

import re
from itertools import accumulate
from datetime import date
    
def find_day(s, pattern=re.compile(r'\d+')): 
    return 99 if not s.strip() else int(p.group(0)) if (p:=pattern.search(s)) else 0

def find_month(previous, s, pattern = re.compile(fr"^\*\*({'|'.join(months_of_year)})")):
    ' Index of Month in year (i.e. 1-12)'
    return months_of_year.index(p.group(1)) if (p:=pattern.search(s)) else previous

with open('test.txt') as infile:
    lines = infile.readlines()
    
months_of_year = [date(2021, i, 1).strftime('%B') for i in range(1, 13)] # Months of year
months = list(accumulate(lines, func = find_month, initial = ''))[1:]   # Create Month for each line
days = (find_day(line) for line in lines)                               # Day for each line

# sort lines based upon it's month and day
result = (x[-1] for x in sorted(zip(months, days, lines), key = lambda x: x[:2]))
    
with open('output.txt', 'w') as outfile:
    outfile.writelines(result)
    

Answer 2

This program runs under Windows or Linux, which have a sort program. It works by reading in each line of the input file and prepending to each line 4 characters, a 2-digit month number and a 2-digit day number (for the blank line between months it uses '99' as the day number so that it follows all the birthdays for the month). It then pipes these modified lines to the sort program and processes the piped output to remove the first 4 characters and to rewrite the file in place , which means you might want to make a backup of the file before running this in case the computer goes down midway in the processing. It shouldn't be too difficult to modify the code to write the output to a separate file.

This technique is used because no assumption is made on the size of the file -- there could be millions of birthdays for a given month. As long as the sort program can handle the input, this program can.

from subprocess import Popen, PIPE
import sys
import re

p = Popen('sort', stdin=PIPE, stdout=PIPE, shell=True, text=True)
month_no = 0
with open('test.txt', 'r+') as f:
    for line in f:
        if " birthdays:**" in line:
            month_no += 1
            p.stdin.write("%02d00" % month_no)
        else:
            m = re.match(r'\*\*(\d+)\*\*', line)
            if m:
                p.stdin.write("%02d%02d" % (month_no, int(m[1])))
            else:
                # blank line?
                p.stdin.write("%02d99" % month_no)
        p.stdin.write(line)
    p.stdin.close()
    f.seek(0, 0) # reposition back to beginning
    for line in p.stdout:
        f.write(line[4:]) # skip over
    f.truncate() # this really shouldn't be necesssary
p.wait()

Answer 3

Using collections.defaultdict will be very handy here so you don't need to do any checking you can just add data. You basically just read the file keeping the current month in a variable and check if you're on a new month or not then if you're on a new month just update it, if you're on a date get the day and append the string. (this allows for multiple people to have the same birthday.

from collections import defaultdict

data = defaultdict(lambda: defaultdict(list))

with open('filename.txt') as infile:
    month = next(infile).strip()
    for line in infile:
        if not line.strip(): continue
        if line[2].isalpha():
            month = line.strip()
        else:
            data[month][int(line.split('**')[1])].append(line.strip())

This gets you data neatly into a dict as shown below based on your example:

{'**January birthdays:**': {17: ['**17** - !@Mark'], 4: ['**4** - !@Jan'], 15: ['**15** - !@Ralph']},
 '**February birthdays:**': {27: ['**27** - !@Steve'], 19: ['**19** - !@Bill'], 29: ['**29** - !@Bob']}}

From here you just loop back through the data and just sort the dates as you loop and write to file.

with open('filename.txt', 'w') as outfile:
    for month, days in data.items():
        outfile.write(month + '\n')
        for day in sorted(days):
            for day_text in days[day]:
                outfile.write(day_text + '\n')
        outfile.write('\n')