python格式化输出之format用法

1 >>> print('{} {}'.format('hello','world')) # 不带字段 
2 hello world 
3 >>> print('{0} {1}'.format('hello','world')) # 带数字编号 
4 hello world 
5 >>> print('{0} {1} {0}'.format('hello','world')) # 打乱顺序 
6 hello world hello 
7 >>> print('{1} {1} {0}'.format('hello','world')) 
8 world world hello 
9 >>> print('{a} {tom} {a}'.format(tom='hello',a='world')) # 带关键字 
10 world hello world

1 >>> print('{} and {}'.format('hello','world')) # 默认左对齐 
2 hello and world 
3 >>> print('{:10s} and {:>10s}'.format('hello','world')) # 取10位左对齐，取10位右对齐 
4 hello and world 
5 >>> print('{:^10s} and {:^10s}'.format('hello','world')) # 取10位中间对齐 
6 hello and world 
7 >>> print('{} is {:.2f}'.format(1.123,1.123)) # 取2位小数 
8 1.123 is 1.12 
9 >>> print('{0} is {0:>10.2f}'.format(1.123)) # 取2位小数，右对齐，取10位 
10 1.123 is 1.12

1 >>> print('{0:b}'.format(3))
2 11
3 >>> print('{:c}'.format(20))
4 
5 >>> print('{:d}'.format(20))
6 20
7 >>> print('{:o}'.format(20))
8 24
9 >>> print('{:x}'.format(20))
10 14
11 >>> print('{:e}'.format(20))
12 2.000000e+01
13 >>> print('{:g}'.format(20.1))
14 20.1
15 >>> print('{:f}'.format(20))
16 20.000000
17 >>> print('{:n}'.format(20))
18 20
19 >>> print('{:%}'.format(20))
20 2000.000000%
21 >>> 

通过位置匹配参数

>>> 
>>> '{0}, {1}, {2}'.format('a', 'b', 'c') 
'a, b, c' 
>>> '{}, {}, {}'.format('a', 'b', 'c') # 3.1+版本支持 
'a, b, c' 
>>> '{2}, {1}, {0}'.format('a', 'b', 'c') 
'c, b, a' 
>>> '{2}, {1}, {0}'.format(*'abc') # 可打乱顺序 
'c, b, a' 
>>> '{0}{1}{0}'.format('abra', 'cad') # 可重复 
'abracadabra'

>>> 'Coordinates: {latitude}, {longitude}'.format(latitude='37.24N', longitude='-115.81W') 'Coordinates: 37.24N, -115.81W' 
>>> coord = {'latitude': '37.24N', 'longitude': '-115.81W'} 
>>> 'Coordinates: {latitude}, {longitude}'.format(**coord) 
'Coordinates: 37.24N, -115.81W'

通过属性匹配参数

>>> c = 3-5j 
>>> ('The complex number {0} is formed from the real part {0.real} ' 
... 'and the imaginary part {0.imag}.').format(c) 
'The complex number (3-5j) is formed from the real part 3.0 and the imaginary part -5.0.' >>> class Point: 
... def __init__(self, x, y): 
... self.x, self.y = x, y 
... def __str__(self): 
... return 'Point({self.x}, {self.y})'.format(self=self) 
... 
>>> str(Point(4, 2)) 
'Point(4, 2)'

通过下标或key匹配参数

>>>
>>> coord = (3, 5)
>>> 'X: {0[0]};  Y: {0[1]}'.format(coord)
'X: 3;  Y: 5'
>>> a = {'a': 'test_a', 'b': 'test_b'}
>>> 'X: {0[a]};  Y: {0[b]}'.format(a)
'X: test_a;  Y: test_b'

占位符%s和%r
replacement_field ::= "{" [field_name] ["!" conversion] [":" format_spec] "}"
conversion ::= "r" | "s" | "a"
这里只有三个转换符号，用"!"开头。
"!r"对应 repr()；"!s"对应 str(); "!a"对应ascii()。

>>> "repr() shows quotes: {!r}; str() doesn't: {!s}".format('test1', 'test2') 
"repr() shows quotes: 'test1'; str() doesn't: test2" # 输出结果是一个带引号，一个不带

设置长度及对齐

>>> '{:<30}'.format('left aligned') # 左对齐

'left aligned                  '
>>> '{:>30}'.format('right aligned')  # 右对齐
'                 right aligned'
>>> '{:^30}'.format('centered')  # 中间对齐
'           centered           '
>>> '{:*^30}'.format('centered')  # 使用“*”填充
'***********centered***********'
>>>'{:0=30}'.format(11)  # 还有“=”只能应用于数字，这种方法可用“>”代替
'000000000000000000000000000011'

%+f, %-f, 和 % f的用法

>>> 
>>> '{:+f}; {:+f}'.format(3.14, -3.14) # 总是显示符号 
'+3.140000; -3.140000' 
>>> '{: f}; {: f}'.format(3.14, -3.14) # 若是+数，则在前面留空格 
' 3.140000; -3.140000' 
>>> '{:-f}; {:-f}'.format(3.14, -3.14) # -数时显示-，与'{:f}; {:f}'一致 
'3.140000; -3.140000'

>>> 
>>> # format also supports binary numbers 
>>> "int: {0:d}; hex: {0:x}; oct: {0:o}; bin: {0:b}".format(42) 
'int: 42; hex: 2a; oct: 52; bin: 101010' 
>>> # with 0x, 0o, or 0b as prefix: >>> "int: {0:d}; hex: {0:#x}; oct: {0:#o}; bin: {0:#b}".format(42) # 在前面加“#”，则带进制前缀 
'int: 42; hex: 0x2a; oct: 0o52; bin: 0b101010'

>>> 
>>> '{:,}'.format(1234567890) 
'1,234,567,890'

百分数%

>>> 
>>> points = 19 
>>> total = 22 
>>> 'Correct answers: {:.2%}'.format(points/total) 
'Correct answers: 86.36%'

时间

>>> 
>>> import datetime 
>>> d = datetime.datetime(2010, 7, 4, 12, 15, 58) 
>>> '{:%Y-%m-%d %H:%M:%S}'.format(d) 
'2010-07-04 12:15:58'

占位符嵌套

>>> 
>>> for align, text in zip('<^>', ['left', 'center', 'right']): 
... '{0:{fill}{align}16}'.format(text, fill=align, align=align) 
... 
'left<<<<<<<<<<<<' 
'^^^^^center^^^^^' 
'>>>>>>>>>>>right' 
>>> 
>>> octets = [192, 168, 0, 1] 
>>> '{:02X}{:02X}{:02X}{:02X}'.format(*octets) 
'C0A80001' 
>>> int(_, 16) # 官方文档给出来的，无法在IDLE复现 
3232235521 
>>> 
>>> width = 5 
>>> for num in range(5,12): 
... for base in 'dXob': 
... print('{0:{width}{base}}'.format(num, base=base, width=width), end=' ') 
... print() 
... 
5 5 5 101 
6 6 6 110 
7 7 7 111 
8 8 10 1000 
9 9 11 1001 
10 A 12 1010 
11 B 13 1011

name = 'jack' 
age = 18 
sex = 'man' 
job = "IT" 
salary = 9999.99 

print(f'my name is {name.capitalize()}.') 
print(f'I am {age:*^10} years old.') print(f'I am a {sex}') 
print(f'My salary is {salary:10.3f}') 

# 结果 
my name is Jack. 
I am ****18**** years old. 
I am a man 
My salary is 9999.990