如何以格式化字符串打开文件？

Question

I have a series of files with lots of variables defined in the form {myvar} inside. eg

file.txt

This is {myvar}.

I want to open them, and have the variables being replaced normally:

with open('path/to/file.txt', 'r') as file:
    myfile = file.read().replace('\n', '')


myvar='myself.'
print(f"{myfile}")

Should output:

This is myself.

How can I open the file as a formatted string? Or convert the string to formatted string?

Answer 1

This seems to work if the variable is local to the call, if it's a global variable, use **globals() . You can also put the value in a dictionary that has the variable name as the key.

myvar = 'myself'
newline = '\n'  # Avoids SyntaxError: f-string expr cannot include a backslash

with open('unformatted.txt', 'r') as file:
    myfile = f"{file.read().replace(newline, '')}".format(**locals())

print(myfile)

Answer 2

You are almost there.

Assume there is "This is {myvar}." in file.txt.

Coding:

with open('path/to/file.txt', 'r') as file:
    myfile = file.read().replace('\n', '')

myvar='myself'

print(myfile.format(myvar=myvar))

Any strings in plain text format, can be imported as a variable from a text file. Then the strings variable can be manipulated as normal.

In you case, the key is "{var}". So you can easily use ".format(var=varx) as long as you defined variable "varx".

Output:

This is myself.

And if you want to import html template with css style and replace some contents, you can just use "{{" and "}}" to escape "{" and "}".

Example 2 In file:

This is {myvar} for a {{var}}.

Output:

This is myself for a {var}.