Python 隨筆 - file management: replace
===
###### tags: `Python`

Method 1 - Does not work
---

import os

f = open("data.txt", 'r')
output = open("data2.txt", 'w')
store = open("data_temp.txt", 'w+')

store.write(f.read().replace("Hand ",''))
output.write(store.read().replace("Material ",''))

f.close()
output.close()
store.close()
os.remove("data_temp.txt")

錯誤原因：
1. 若要重複讀取檔案，需要將指標回歸至檔案頭(自己的假設)
解決方法：在閱讀完畢執行 `f1.seek(0)`
1. 多執行緒問題
>就是你有一個中間檔，第一次取代完存在裡面，第二次取代的時候讀出，不過python的檔案讀寫不是原子性的，義思就是他可能在底層對某個檔案的讀寫是同時進行的，然後就會混亂XD
>[:linked_paperclips: stackoverflow.com/questions/1185660](https://stackoverflow.com/questions/1185660/python-is-os-read-os-write-on-an-os-pipe-threadsafe)
1. 檔案權限，參考以下網友整理不同Mode給予的權限

    |          Mode          |  r   |  r+  |  w   |  w+  |  a   |  a+  |
    | :--------------------: | :--: | :--: | :--: | :--: | :--: | :--: |
    |          Read          |  +   |  +   |      |  +   |      |  +   |
    |         Write          |      |  +   |  +   |  +   |  +   |  +   |
    |         Create         |      |      |  +   |  +   |  +   |  +   |
    |         Cover          |      |      |  +   |  +   |      |      |
    | Point in the beginning |  +   |  +   |  +   |  +   |      |      |
    |    Point in the end    |      |      |      |      |  +   |  +   |

[:linked_paperclips: stackoverflow.com/questions/6648493/](https://stackoverflow.com/questions/6648493/how-to-open-a-file-for-both-reading-and-writing)

Method 2 - Dummy answer to fix Method 1
---

import os
f = open("data.txt", 'r')
output = open("data2.txt", 'w')
store = open("data_temp.txt", 'w')
store.write(f.read().replace("Hand ",''))
store.close()
store = open("data_temp.txt", 'r')
output.write(store.read().replace("Material ",''))
f.close()
output.close()
store.close()
# if os.path.exists("demofile.txt"):
os.remove("data_temp.txt") # one file at a time

Method 3 - Works well
---

checkWords = ("Hand ","Material ")
repWords = ("","")
f1 = open('data.txt', 'r')
f2 = open('data2.txt', 'w')
for line in f1:
    for check, rep in zip(checkWords, repWords):
        line = line.replace(check, rep)
    f2.write(line)
f1.close()
f2.close()

[:linked_paperclips: stackoverflow.com/questions/51240862/](https://stackoverflow.com/questions/51240862/find-and-replace-multiple-words-in-a-file-python)

Method 4
---

import re
s = "old_text1 old_text2"
s1 = re.sub("old_text" , "new_text" , s)

[:linked_paperclips: stackoverflow.com/questions/51240862/](https://stackoverflow.com/questions/51240862/find-and-replace-multiple-words-in-a-file-python)

Method 5
---

def replace_all(text, dic):
    # for i, j in dic.iteritems():
    for i, j in dict.items(): #dict.items() for python 3
        text = text.replace(i, j)
    return text

[:linked_paperclips: stackoverflow.com/questions/51240862/](https://stackoverflow.com/questions/51240862/find-and-replace-multiple-words-in-a-file-python)