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 · Accepted Answer · 2022-02-01 12:35:51Z

1

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)

edited Feb 1, 2022 at 12:35

answered Feb 1, 2022 at 12:15

Shanavas M

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1 Comment

fateme.ata Over a year ago

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.

chillking · Accepted Answer · 2022-02-01 12:09:00Z

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 1, 2022 at 12:09

chillking

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2 Comments

fateme.ata Over a year ago

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.

chillking Over a year ago

@Shanavas M was faster than me!

fateme.ata · Accepted Answer · 2022-02-02 12:30:55Z

0

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)

answered Feb 2, 2022 at 12:30

fateme.ata

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1 Comment

Community Over a year ago

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