Python/Django新手求教：如何替换三引号字符串中的变量值？

Hey there! Let's break down how this string replacement works—it's a core Python feature you'll rely on constantly as you build Django projects.

What's Going On With This Code? #

The key here is Python's str.format() method, which handles replacing placeholder values in your VCard template string. Here's a step-by-step breakdown:

1. The Multi-Line Template String
   You're using triple quotes (""") to define a multi-line string that matches the VCard format exactly. The {first_name}, {last_name}, and other bracketed terms are placeholders—they act as markers for values you'll inject later. Triple quotes are ideal here because they let you write the VCard structure with proper newlines, no messy string concatenation or escape characters needed.

2. The format() Method in Action
   When you call person_output.format(...), you pass in key-value pairs where each key matches a placeholder name in the template. Python scans the string and replaces every {placeholder} with the corresponding value you provided. For example:

   • {first_name} gets swapped out for person.first_name (the first name field from your Django Person model instance)
   • {rev} is replaced with the formatted timestamp generated by d.strftime('%Y%M%d%H%f')

3. Django Context Basics
   The queryset comes from Django's admin interface—it's a collection of your model instances. When you loop through queryset.all(), each person is an instance of your Django model, so you can access its fields directly using dot notation (like person.phone or person.email). This is standard Django ORM behavior for working with model data.

Relevant Official Docs #

• Python str.format(): The Python official docs have a detailed section on string formatting that covers everything from basic placeholder replacement to advanced format specifiers (like formatting numbers or dates).
• Django Model Instances: The Django documentation explains how to access model fields, work with QuerySets, and interact with model instances—this is foundational knowledge for building Django apps.

Quick Bonus Tip #

If you're using Python 3.6+, you can use f-strings for even more concise formatting. Your template could be rewritten like this (though the format() approach is still totally valid, especially if you need to reuse the template elsewhere):

person_output = f"""BEGIN:VCARD
VERSION:3.0
N:{person.last_name};{person.first_name}
FN:{person.first_name} {person.last_name}
TEL;TYPE=HOME,VOICE:{person.phone}
TEL;TYPE=WORK,VOICE:{person.secondary_phone}
EMAIL:{person.email}
REV:{d.strftime('%Y%M%d%H%f')}
END:VCARD"""

内容的提问来源于stack exchange，提问作者mehdi