使用 str.format() 访问对象属性

问题描述

限时删除！！

我有一个带有 a、b、c 属性的 Python 对象.

我仍然使用旧的字符串格式，所以我通常会手动打印这些:

 print '我的对象有字符串 a=%s, b=%s, c=%s' % (obj.a, obj.b, obj.c)

最近，我的字符串变得超长，我更愿意将对象简单地传递给字符串格式函数，例如:

 print '我的对象有字符串 a=%a, b=%b, c=%c'.format(obj)

但是，语法不正确.这可能吗?

解决方案

您可以在格式字段本身内使用 .attribute_name 符号:

print '我的对象有字符串 a={0.a}, b={0.b}, c={0.c}'.format(obj)

以下是演示:

>>>类测试(对象):... def __init__(self, a, b, c):... self.a = a... self.b = b... self.c = c...>>>obj = 测试(1、2、3)>>>'我的对象有字符串 a={0.a}, b={0.b}, c={0.c}'.format(obj)'我的对象有字符串 a=1, b=2, c=3'>>>

但是请注意，执行此操作时确实需要对格式字段进行编号.此外，如您所见，str.format 函数的格式字段由大括号 {...} 表示，而不是 %签名.

有关详细信息，请参阅 Python 中的格式字符串语法的参考.

I have a Python object with attributes a, b, c.

I still use old string formatting, so I'd normally print these manually:

 print 'My object has strings a=%s, b=%s, c=%s' % (obj.a, obj.b, obj.c)

Lately, my strings have been getting super long, and I'd much rather be able to simply pass the object into a string format function, something like:

 print 'My object has strings a=%a, b=%b, c=%c'.format(obj)

However, the syntax is incorrect. Is this possible?

解决方案

You can use the .attribute_name notation inside the format fields themselves:

print 'My object has strings a={0.a}, b={0.b}, c={0.c}'.format(obj)

Below is a demonstration:

>>> class Test(object):
...     def __init__(self, a, b, c):
...         self.a = a
...         self.b = b
...         self.c = c
...
>>> obj = Test(1, 2, 3)
>>> 'My object has strings a={0.a}, b={0.b}, c={0.c}'.format(obj)
'My object has strings a=1, b=2, c=3'
>>>

Note however that you do need to number the format fields when doing this. Also, as you can see, the str.format function has its format fields denoted by curly braces {...}, not the % sign.

For more information, here is a reference on the Format String Syntax in Python.

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