相对基本格式化输出采用‘%’的方法，format()功能更强大，该函数把字符串当成一个模板，通过传入的参数进行格式化，并且使用大括号‘{}’作为特殊字符代替‘%’
（1）不带编号，即“{}”
（2）带数字编号，可调换顺序，即“{1}”、“{2}”
（3）带关键字，即“{a}”、“{tom}”
1 >>> print(‘{} {}‘.format(‘hello‘,‘world‘)) # 不带字段 2 hello world 3 4 >>> print(‘{0} {1}‘.format(‘hello‘,‘world‘)) # 带数字编号 5 hello world 6 7 >>> print(‘{0} {1} {0}‘.format(‘hello‘,‘world‘)) # 打乱顺序 8 hello world hello 9 10 >>> print(‘{1} {1} {0}‘.format(‘hello‘,‘world‘)) 11 world world hello 12 13 >>> print(‘{a} {tom} {a}‘.format(tom=‘hello‘,a=‘world‘)) # 带关键字 14 world hello world
1 >>> ‘{0}, {1}, {2}‘.format(‘a‘, ‘b‘, ‘c‘) 2 ‘a, b, c‘ 3 4 >>> ‘{}, {}, {}‘.format(‘a‘, ‘b‘, ‘c‘) # 3.1+版本支持 5 ‘a, b, c‘ 6 7 >>> ‘{2}, {1}, {0}‘.format(‘a‘, ‘b‘, ‘c‘) 8 ‘c, b, a‘ 9 10 >>> ‘{2}, {1}, {0}‘.format(*‘abc‘) # 可打乱顺序 11 ‘c, b, a‘ 12 13 >>> ‘{0}{1}{0}‘.format(‘abra‘, ‘cad‘) # 可重复 14 ‘abracadabra‘
>>> 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)‘
>>> 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‘
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%
>>> "{0} {1}".format("hello","world") ‘hello world‘ # f"xxxx" # 可在字符串前加f以达到格式化的目的，在{}里加入对象，此为format的另一种形式： >>> a = "hello" >>> b = "world" >>> f"{a} {b}" ‘hello world‘ 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
>>> # 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‘
（1）< （默认）左对齐、> 右对齐、^ 中间对齐、= （只用于数字）在小数点后进行补齐
（2）取位数“{:4s}”、"{:.2f}"等
>>> print(‘{} and {}‘.format(‘hello‘,‘world‘)) # 默认左对齐 hello and world
>>> print(‘{:10s} and {:>10s}‘.format(‘hello‘,‘world‘)) # 取10位左对齐，取10位右对齐 hello and world
>>> print(‘{:^10s} and {:^10s}‘.format(‘hello‘,‘world‘)) # 取10位中间对齐 hello and world
>>> print(‘{} is {:.2f}‘.format(1.123,1.123)) # 取2位小数 1.123 is 1.12
>>> print(‘{0} is {0:>10.2f}‘.format(1.123)) # 取2位小数，右对齐，取10位 1.123 is 1.12 >>> ‘{:<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}‘.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‘
>>> ‘{:+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‘
>>> 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‘
>>> ‘{:,}‘.format(1234567890) ‘1,234,567,890‘
>>> 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
""" 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
原文：https://www.cnblogs.com/wenfang0811/p/14151126.html