CODEWITHSUNDEEP
pythonstringreplace
user15809251
user15809251

Reputation:

Python placeholders in read text

I am fairly new to Python, teaching it to myself by watching tutorials and doing the trial and error kind of thing, and I ran into a task, which I am not able to solve right now:

I am reading from a file with following code:

def read_file(file):
    try:
        with open(file) as f:
            content = f.read()
            return content
    except FileNotFoundError:
        print("\nThis file does not exist!")
        exit()

The file(.txt) I am reading contains a text with multiple placeholders:

Hello {name}, you are on {street_name}!

Now I want to replace the placeholders {name} and {street_name} with their corresponding variables.

I know how f-strings work. Can this somehow be applied to this problem too, or do I have to parse the text to find the placeholders and somehow find out the fitting variable that way?

Each text I read, contains different placeholders. So I have to find out, which placeholder it is and replace it with the according string.

Upvotes: 2

Views: 923

Answers (2)

Igor Shavrin
Igor Shavrin

Reputation: 1

Here is a solution similar to that proposed by @Timus, but completely avoiding regular expressions.

This works in case you have a dictionary of known placeholders, and want to use it with an input text containing unknown placeholders that are to be replaced with a default text.

from collections import defaultdict

input_string = "The quick {color} fox {action} over the {adjective} dog."

placeholders = defaultdict(
    lambda: "UNKNOWN",
    color='brown',
    action='jumps',
    animal='fox'
)

print(input_string.format_map(placeholders))

#>> The quick brown fox jumps over the UNKNOWN dog.

Upvotes: 0

Timus
Timus

Reputation: 11321

Not sure if that is what you are looking for:

string = "Hello {name}, you are on {street_name}!"
string = string.format(name="Joe", street_name="Main Street")
print(string)

or

string = "Hello {name}, you are on {street_name}!"
name = "Joe"
street_name = "Main Street"
string = string.format(name=name, street_name=street_name)
print(string)

gives you

Hello Joe, you are on Main Street!

See here.

If you actually don't know what placeholders are in the text then you could do something like:

import re

string = "Hello {name}, you are on {street_name}!"
name = "Joe"
street_name = "Main Street"

placeholders = set(re.findall(r"{(\w+)}", string))
string = string.format_map({
    placeholder: globals().get(placeholder, "UNKOWN")
    for placeholder in placeholders
})

If you know that all placeholders are present as variables, then you could simply do:

string = "Hello {name}, you are on {street_name}!"
name = "Joe"
street_name = "Main Street"

string = string.format_map(globals())

Upvotes: 2

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