Python Read and Write files

Question

I have 1,000 odd files that I am trying to concatenate into one large file. They are all .txt files and all contain the same data format.

I seem to be able to use PyCharm to read each line in each file, and write it to an output file. I count the number of lines and it comes out to be around 393,225 which is roughly accurate (I haven't manually counted). However, when I count the number of lines in the output file, it is only 401 and I don't know why it hasn't done them all.....

Here is the current code I am using in Python:

import datetime
from pathlib import Path

start_date = datetime.date(year=2019, month=3, day=22)
end_date = datetime.date(year=2015, month=12, day=1)

list = []

if start_date == end_date:
    for n in range((end_date - start_date).days + 1):
        list.append(start_date + datetime.timedelta(n))
else:
    for n in range((start_date - end_date).days + 1):
        list.append(start_date - datetime.timedelta(n))

countFile = 0
countLines = 0

for d in reversed(list):
    date = str(d)
    path = '/Users/stephankokkas/notuploading/TESTFILES/PRICEDATA/' + date + '/Race.txt'

    raceFile = Path(path)
    if raceFile.is_file():

        with open('/Users/stephankokkas/notuploading/TESTFILES/finalRaceFile/FinalRace.txt', 'w') as outfile:
            with open(path) as infile:
                for line in infile:
                    outfile.write(line)
                    countLines = countLines + 1
                    print(line)
    else:
        print("file NOT FOUND")



print(countLines)

countLines = 0
with open('/Users/stephankokkas/notuploading/TESTFILES/finalRaceFile/FinalRace.txt', 'r') as infile:
    for line in infile:
        countLines = countLines + 1
print(countLines)

And here is the output

393225
401

I am not sure why they are not the same number.... I expect them to be.

When I open the output file, the data only ranges from 2019-03-22 to 2019-03-22

it seems to only be doing the last file it finds.

Most likely something obvious, but some help would be good. Thanks

Possible duplicate of [How do you append to a file in Python?](https://stackoverflow.com/questions/4706499/how-do-you-append-to-a-file-in-python) — Sayse, May 09 '19 at 14:46
Tl;dr, you're using the wrong write mode for writing to `FinalRace.txt` use `a` instead of `w` — Sayse, May 09 '19 at 14:50
as advice: don't use list as a variable name - python lets you do it, but you are re-assigning a python class as a variable — Stael, May 09 '19 at 14:54

score 0 · Accepted Answer · answered May 09 '19 at 14:50

0

When you open the file with 'w' mode you overwrite it. You need to open with 'a' mode to append.

e.g.

with open('fielname.txt', 'a') as outfile:

See the docs

answered May 09 '19 at 14:50

Mikey Lockwood

1,258
1
9
22

Python Read and Write files

1 Answers1