为什么我会在 Python 字符串格式中使用 %r 以外的任何东西? [英] Why would I ever use anything else than %r in Python string formatting?
问题描述
我偶尔会使用 Python 字符串格式.可以这样做:
print('int: %i.Float: %f.String: %s' % (54, 34.434, 'some text'))
但是,这也可以这样做:
print('int: %r. Float: %r. String: %r' % (54, 34.434, 'some text'))
以及使用 %s:
print('int: %s. Float: %s. String: %s' % (54, 34.434, 'some text'))
因此,我的问题是:为什么我要使用 %r 或 %s 以外的任何东西?其他选项(%i、%f 和 %s)对我来说似乎没什么用,所以我想知道为什么每个人都会使用它们?
添加了带有 %s 的示例
对于浮点数,repr
和 str
的值可以不同:
对字符串使用 %r
将导致它周围有引号:
您应该始终将 %f
用于浮点数,%d
用于整数.
I occasionally use Python string formatting. This can be done like so:
print('int: %i. Float: %f. String: %s' % (54, 34.434, 'some text'))
But, this can also be done like this:
print('int: %r. Float: %r. String: %r' % (54, 34.434, 'some text'))
As well as using %s:
print('int: %s. Float: %s. String: %s' % (54, 34.434, 'some text'))
My question is therefore: why would I ever use anything else than the %r or %s? The other options (%i, %f and %s) simply seem useless to me, so I'm just wondering why anybody would every use them?
[edit] Added the example with %s
For floats, the value of repr
and str
can vary:
>>> num = .2 + .1
>>> 'Float: %f. Repr: %r Str: %s' % (num, num, num)
'Float: 0.300000. Repr: 0.30000000000000004 Str: 0.3'
Using %r
for strings will result in quotes around it:
>>> 'Repr:%r Str:%s' % ('foo','foo')
"Repr:'foo' Str:foo"
You should always use %f
for floats and %d
for integers.
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