python string find and replace in text file

Question

I'm reading a file and replacing a text string. I'm doing this for a few different strings, I know this isn't the most effeciant code I'm just trying to get it working. Here's what I have:

    for line in fileinput.input(new_config, inplace=1):
        print line.replace("http://domain.com", self.site_address)
        print line.replace("dbname", self.db_name)
        print line.replace("root", self.db_user)
        print line.replace("password", self.db_pass)
        print line.replace("smvc_", self.prefix

this works but it also writes every line in the file 5 times and only replaces the string on the first attempt on not on the new lines it creates (doesn't matter if it matches the string or not)

SuperBiasedMan · Accepted Answer · 2015-06-18 13:48:09Z

4

You just need to treat it as one string and apply all replacements to it.

for line in fileinput.input(new_config, inplace=1):
    line = line.replace("http://domain.com", self.site_address)
    line = line.replace("dbname", self.db_name)
    line = line.replace("root", self.db_user)
    line = line.replace("password", self.db_pass)
    line = line.replace("smvc_", self.prefix)
    print line

If it doesn't find any of those targets it will just not make any change to the line string so it will just replace what it DOES find.

answered Jun 18, 2015 at 13:48

SuperBiasedMan

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SuperBiasedMan · Accepted Answer · 2015-06-18 14:50:04Z

2

for line in fileinput.input(new_config, inplace=1):
    print line.replace(
        "http://domain.com", self.site_address).replace(
        "dbname", self.db_name).replace(
         "root", self.db_user).replace(
         "password", self.db_pass).replace("smvc_", self.prefix)

Done by copying and pasting what you wrote and using only the delete key and re-indenting. No characters added except the last closing paren.

Alternatively, this format may be clearer. It uses the backslash character to split the one line in a neater way, for better readability:

    print line.replace("http://domain.com", self.site_address) \
              .replace("dbname", self.db_name) \
              .replace("root", self.db_user) \
              .replace("password", self.db_pass) \
              .replace("smvc_", self.prefix)

edited Jun 18, 2015 at 14:50

SuperBiasedMan

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answered Jun 18, 2015 at 13:48

jrwren

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Comments

Tenzin · Accepted Answer · 2015-06-18 13:56:54Z

-1

You can read a file line by line.
And at every line look for the word you would like to replace.

For example:

line1 = 'Hello World There'
def Dummy():
    lineA = line1.replace('H', 'A')
    lineB = lineA.replace('e', 'o')
    print(lineB)

Dummy()

Then wirte lineB to a file.

edited Jun 18, 2015 at 13:56

answered Jun 18, 2015 at 13:51

Tenzin

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3 Comments

Tenzin Over a year ago

And again a downvote without a comment. -_- My example does what the topic starter is asking for, just on a different way.... What is wrong with that? demotivating

SuperBiasedMan Over a year ago

Your solution uses a redundant function. Dummy can only operate on line1 so why bother putting it in a function in the first place? It's probably not worthwhile (in this particular case) to have different variables for each replacement either.

Tenzin Over a year ago

If you read the first lines you see it should be used by a function that reads in a file line by line.. While it is reading every line then do a replace. So line1 replesents the current line from the file that is being read.

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