如何在 Python 中 X 次后替换文件中的字符串？

Question

Premise Explaination:

I have this Python script Main.py that gathers distance and temperature and sends them to a text file, Data.txt. Currently I have it so that it replaces the string of text each time

EDIT:

Currently it is only printing one string of text and the code repeatedly overwrites this one line, what I want is for the code to print 10 lines of that string of text before overwriting the oldest line, just like in the example below.

Example:

# Main.py

while True:
    f=open("data.txt","a+")
    a = str(scan())+"\n"
    f.write(a);
    log.log("Wrote to file")
    log.log(a)
    with open("data.txt","rt") as fin:
        with open("data.txt","wt")as fout:
            for line in fin:
                fout.write(line.replace("scan()", "scan()"))
    f.close()

Actual Output:

[26.07, 32.31, 93.73, False] #it constantly overwrites this line.

Question:

How do I make it so that it prints out at least 10 lines of text before replacing the string?

Needed Output Example:

    #print out 10 strings of text
    [23.07, 32.31, 93.73, False] 
    [27.03, 36.34, 93.73, False] 
    [26.07, 34.36, 93.73, False] 
    [28.02, 32.21, 93.73, False] 
    [24.03, 22.31, 93.73, False] 
    [22.07, 28.31, 93.73, False] 
    [29.04, 32.21, 93.73, False] 
    [26.07, 32.31, 93.73, False] 
    [26.07, 32.31, 93.73, False] 
    [26.07, 32.31, 93.73, False]

#new string of text comes in [26.07, 32.31, 93.73, True]
expected output:
   [27.03, 36.34, 93.73, False] 
   [26.07, 34.36, 93.73, False] 
   [28.02, 32.21, 93.73, False] 
   [24.03, 22.31, 93.73, False] 
   [22.07, 28.31, 93.73, False] 
   [29.04, 32.21, 93.73, False] 
   [26.07, 32.31, 93.73, False] 
   [26.07, 32.31, 93.73, False] 
   [26.07, 32.31, 93.73, False] 
   [26.07, 32.31, 93.73, True]  # replaces the string one, adding this new data into the list.

Answer 1

You might consider using time.sleep() so that you only write to the file every second or so.

import time
import numpy as np

def scan():
    # your scanner here. 
    return list(np.random.randint(1, 10, 4))

a_list = list()

while True:
    a = str(scan()) + "\n"
    a_list.insert(0, a)
    a_list = a_list[:10]

    with open("data.txt", "wt") as fout:
        fout.write(''.join(a_list))
        time.sleep(1)

Answer 2

Try this:

while True:
    txt = open("data.txt", "r").read()
    txt = txt.split("\n")
    if len(txt) == 10:
        txt.pop(0)
        txt.append("what you want to write")
    else:
        txt.append("what you want to write")
    f = open("data.txt", "w")
    f.write("\n".join(txt))