%和%d是格式说明符或占位符，用于格式化字符串、小数、浮点数等。

最常用的格式说明符:

% s:字符串

% d:小数

% f:浮动

自解释代码:

name = "Gandalf"
extendedName = "the Grey"
age = 84
IQ = 149.9
print('type(name): ', type(name)) # type(name): <class 'str'>
print('type(age): ', type(age))   # type(age): <class 'int'>
print('type(IQ): ', type(IQ))     # type(IQ): <class 'float'>

print('%s %s\'s age is %d with incredible IQ of %f ' %(name, extendedName, age, IQ)) # Gandalf the Grey's age is 84 with incredible IQ of 149.900000

# The same output can be printed in following ways:


print ('{0} {1}\'s age is {2} with incredible IQ of {3} '.format(name, extendedName, age, IQ))          # With the help of an older method
print ('{} {}\'s age is {} with incredible IQ of {} '.format(name, extendedName, age, IQ))          # With the help of an older method

print("Multiplication of %d and %f is %f" %(age, IQ, age*IQ)) # Multiplication of 84 and 149.900000 is 12591.600000

# Storing formattings in a string

sub1 = "python string!"
sub2 = "an arg"

a = "I am a %s" % sub1
b = "I am a {0}".format(sub1)

c = "with %(kwarg)s!" % {'kwarg':sub2}
d = "with {kwarg}!".format(kwarg=sub2)

print(a)  # "I am a python string!"
print(b)  # "I am a python string!"
print(c)  # "with an arg!"
print(d)  # "with an arg!"

这是Python 3中的一个很好的例子。

>>> a = input("What is your name? ")
What is your name? Peter

>>> b = input("Where are you from? ")
Where are you from? DE

>>> print("So you are %s of %s." % (a, b))
So you are Peter of DE.

%和%d是格式说明符或占位符，用于格式化字符串、小数、浮点数等。

最常用的格式说明符:

% s:字符串

% d:小数

% f:浮动

自解释代码:

name = "Gandalf"
extendedName = "the Grey"
age = 84
IQ = 149.9
print('type(name): ', type(name)) # type(name): <class 'str'>
print('type(age): ', type(age))   # type(age): <class 'int'>
print('type(IQ): ', type(IQ))     # type(IQ): <class 'float'>

print('%s %s\'s age is %d with incredible IQ of %f ' %(name, extendedName, age, IQ)) # Gandalf the Grey's age is 84 with incredible IQ of 149.900000

# The same output can be printed in following ways:


print ('{0} {1}\'s age is {2} with incredible IQ of {3} '.format(name, extendedName, age, IQ))          # With the help of an older method
print ('{} {}\'s age is {} with incredible IQ of {} '.format(name, extendedName, age, IQ))          # With the help of an older method

print("Multiplication of %d and %f is %f" %(age, IQ, age*IQ)) # Multiplication of 84 and 149.900000 is 12591.600000

# Storing formattings in a string

sub1 = "python string!"
sub2 = "an arg"

a = "I am a %s" % sub1
b = "I am a {0}".format(sub1)

c = "with %(kwarg)s!" % {'kwarg':sub2}
d = "with {kwarg}!".format(kwarg=sub2)

print(a)  # "I am a python string!"
print(b)  # "I am a python string!"
print(c)  # "with an arg!"
print(d)  # "with an arg!"

安德鲁的回答很好。

为了帮助你，这里是你如何在一个字符串中使用多种格式:

"Hello %s, my name is %s" % ('john', 'mike') # Hello john, my name is mike".

如果使用int型而不是字符串，请使用%d而不是%s。

"My name is %s and I'm %d" % ('john', 12) #My name is john and I'm 12

format方法在Python 2.6中引入。它的功能更强，使用起来也不是更难:

>>> "Hello {}, my name is {}".format('john', 'mike')
'Hello john, my name is mike'.

>>> "{1}, {0}".format('world', 'Hello')
'Hello, world'

>>> "{greeting}, {}".format('world', greeting='Hello')
'Hello, world'

>>> '%s' % name
"{'s1': 'hello', 's2': 'sibal'}"
>>> '%s' %name['s1']
'hello'

%s表示使用Python的字符串格式化功能时字符串的转换类型。更具体地说，%s使用str()函数将指定的值转换为字符串。将其与使用repr()函数进行值转换的%r转换类型进行比较。

看一看字符串格式化的文档。