python replace multiple string in a text file

Question

I have a text file which contains this information:

 network={
      ssid="WIFI_SSID"
      scan_ssid=1
      psk="WIFI_PASSWORD"
      key_mgmt=WPA-PSK
}

I want to modify this text file and change the ssid and psk values. so I want something like this:

network={
      ssid="KB150"
      scan_ssid=1
      psk="testpass"
      key_mgmt=WPA-PSK
}

I wrote this code, but it only can add a new line at end of the file only for ssid (something like ssid= KB150):

if __name__ == '__main__':
    ssid = "KB150"
    password = "testpass"
    with open("example.txt", 'r+') as outfile:
        for line in outfile:
            if line.startswith("ssid"):
                sd = line.split("= ")
                outfile.write(line.replace(sd[1], ssid))
            if line.startswith("password"):
                pw = line.split("= ")
                line.replace(pw[1], password)
                outfile.write(line.replace(pw[1], ssid))

    outfile.close()

The values of ssid and psk change whenever a user enter an input in my program, so I need to find the line that starts with those keywords and change their values.

Shanavas M · Answer 1 · 2022-02-01T12:35:51.220

Since the file is small, you can read it fully, do the replacement and write back. You don't have to close it explicitly as with handles it.

if __name__ == '__main__':
    ssid = "KB150"
    password = "testpass"
    # open for reading
    with open("example.txt", 'r') as infile:
        content = infile.read()
    # reopen it for writing
    with open("example.txt", 'w') as outfile:
        content = content.replace("WIFI_SSID", ssid).replace("WIFI_PASSWORD", password)
        outfile.write(content)

Modifying file while reading is tricky. Discussed here

Edit

There are multiple ways to handle it. You can keep a template file with the content.

network={

      ssid="WIFI_SSID"
      scan_ssid=1
      psk="WIFI_PASSWORD"
      key_mgmt=WPA-PSK
}

The script can read the content of template file, replace ssid and password and write to target file.

Another way is to use regex replacement like

import re
if __name__ == '__main__':
    ssid = "KB150"
    password = "testpass"

    with open("example.txt", 'r') as infile:
        content = infile.read()

    # reopen it for writing
    with open("example.txt", 'w') as outfile:
        content = re.sub('ssid="[^"]*"', f'ssid="{ssid}"', content)
        content = re.sub('psk="[^"]*"', f'psk="{password}"', content)
        outfile.write(content)

Useful tip. thanks. But I need to change this file multiple times, every time I want to connect to wifi, so, I need to find a line which starts with "ssid" and "password" and change them, these values are not fixed. — fateme.ata, Feb 01 '22 at 12:19

score 0 · Answer 2 · answered Feb 01 '22 at 12:09

0

I would guess your line.startswith("ssid") is not returning True, because in your example.txt are whitespaces before "ssid". So you maybe want to think about spliting the line with the right amound of whitespaces or search for ssid in every line.

answered Feb 01 '22 at 12:09

chillking

311
1
9

I had some changes in my example here. In my text file, I only create a file with two lines like this: ---- ssid= "WIFI_SSID" password= "WIFI_PASSWORD" ---- still, cannot change the values of them. – fateme.ata Feb 01 '22 at 12:13
@Shanavas M was faster than me! – chillking Feb 01 '22 at 12:19

score 0 · Answer 3 · answered Feb 02 '22 at 12:30

Thanks to Shanavas M (having his useful tip in my mind), My friend helped me and I got finally what I want:)

fileName = 'example.txt'
    result = ""
    ssid = "KB150"
    password = "testpass"

    with open(fileName, 'r') as filehandle:
        for line in filehandle:
            temp = line.split('=')[0]
            if temp == "ssid ":
                result += 'ssid = "{}"\n'.format(ssid)
            elif temp == 'password ':
                result += 'password = "{}"\n'.format(password)
            else:
                result += line

    with open(fileName, 'w') as filehandle:
        filehandle.write(result)

As it’s currently written, your answer is unclear. Please [edit] to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers [in the help center](/help/how-to-answer). — Community, Feb 02 '22 at 12:55

python replace multiple string in a text file

3 Answers3

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