%s用str()方法处理对象

有些情况下，两者处理的结果是一样的，比如说处理int型对象。

例一：

print ("I am %d years old." % 22)
print ("I am %s years old." % 22)  
print ("I am %r years old." % 22)

#输出：
I am 22 years old.  
I am 22 years old.  
I am 22 years old.  

另外一些情况两者就不同了

例二：

'''
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'''
text = "I am %d years old." % 22  
print ("I said: %s." % text)  
print ("I said: %r." % text)  

#输出：
I said: I am 22 years old..
I said: 'I am 22 years old.'. # %r 给字符串加了单引号  

再看一种情况

例三：

>> from datetime import datetime 
>> timeinfo = datetime.today()

>> timeinfo
datetime.datetime(2020, 1, 1, 1, 17, 34, 925488)
>> type(timeinfo)
datetime.datetime

>> repr(timeinfo)
'datetime.datetime(2020, 1, 1, 1, 17, 34, 925488)'
>> str(timeinfo)
'2020-01-01 01:17:34.925488'

%r会将后面给的参数原样打印出来，带有类型信息。

formatter = "%r %r %r %r"
 
print (formatter % (1, 2, 3, 4))
print (formatter % ("one", "two", "three", "four"))
print (formatter % (True, False, False, True))
print (formatter % (formatter, formatter, formatter, formatter))
print (formatter % (
"I had this thing.",
"That you could type up right.",
 "But it didn't sing.",
 "So I said goodnight."
 ))

#输出：
1 2 3 4
'one' 'two' 'three' 'four'
True False False True
'%r %r %r %r' '%r %r %r %r' '%r %r %r %r' '%r %r %r %r'
'I had this thing.' 'That you could type up right.' "But it didn't sing." 'So I said goodnight.'

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