问题

EDITED

I have to format a string with values from a dictionary but the string already contains curly brackets. E.g.:

raw_string = """
    DATABASE = {
        'name': '{DB_NAME}'
   }
"""

But, of course, raw_string.format(my_dictionary) results in KeyErro.

Is there a way to use different symbols to use with .format()?

This is not a duplicate of How can I print literal curly-brace characters in python string and also use .format on it? as I need to keep curly brackets just as they are and use a different delimiter for .format.

回答1:

Using custom placeholder tokens with python `string.format()`

Context

python 2.7
string.format()
alternative approach that allows custom placeholder syntax

Problem

We want to use custom placeholder delimiters with python str.format()

string.format() is powerful, but no native support for placeholder delimiter modification.
string.format() uses curly-brace which is very common and and causes Delimiter collision
string.format() default workaround is to double-up the delimiters, which can be cumbersome.

Solution

We write a custom class that extends native python str.format()

extend native python string.Formatter with custom class
configure string.format() to support arbitrary delimiter placeholder syntax
permit other enhancements such as custom formatters and filters

Example001: Demo use of a custom `ReFormat` class

we wrote a custom ReFormat class that extends python str.format()

# import custom class
import ReFormat

# prepare source data
odata = { "fname" : "Planet",
          "lname" : "Earth",
          "age"   : "4b years",
         }

# format output using .render() 
# method of custom ReFormat class
#
vout = ReFormat.String("Hello &lt;%fname%&gt; &lt;%lname%&gt;!",odata).render()
print(vout)

Pitfalls

requires extension class to str.format()
not intended as a substitute for full-blown sandbox-compatible templating solution

回答2:

I don't think it is possible to use alternative delimiters. You need to use double-curly braces {{ }} for curly braces that you don't want to be replaced by format():

inp = """
DATABASE = {{
    'name': '{DB_NAME}'
}}"""

dictionary = {'DB_NAME': 'abc'}
output = inp.format(**dictionary)
print(output)

Output

DATABASE = {
    'name': 'abc'
}

来源：https://stackoverflow.com/questions/35574349/python-format-string-with-custom-delimiters

标签

python

syntax

format

string-interpolation

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