.f' '或者.F' '或者string.format(args)

1，格式化字符串

{var} 作为占位符

	Year = 2020f 'Today is {Year}'# f.'my py coding... {var}'  F.'my py coding {var}''the sum of 1 + 2 is {0}'.format(1+2)

百分数，小数的格式化

def test_f():import mathprint(f'{math.pi:0.2f}') # 保持小数点后两位test_f()def test_format():print('{:}'.format(99))  # : 可以作为占位符print('{:5}'.format(99)) # 让99的字符宽度为5print('{:0.1%}'.format(0.3)) # 保留百分数后一位小数test_format()'''
3.14
9999
30.0%
'''

：加数字用于对齐

def test_tidy():D = {'name': 'jack', 'age': 19, 'gender': 'male'}for k, v in D.items():print('{0:10} ==> {1}'.format(k, v))'''
name       ==> jack
age        ==> 19
gender     ==> male
'''

!a !r !s 转化为字符串后输出

>>> var = 'sexy'
>>> print(f'She is so {var}.')   
She is so sexy.
>>> print(f'She is so {var!s}.')
She is so sexy.
>>> print(f'She is so {var!r}.')
She is so 'sexy'.

2，str() 和 repr()
str(obj) 返回可读字符串，repr(obj)返回机器可读的表示,两者对于/或者\都不会转义，将对象转换为字符串。

>>> list = ['i', 'dare', 'you'] 
>>> str(list)
"['i', 'dare', 'you']"
>>> repr(list)
"['i', 'dare', 'you']"

3，string.format()方法的详细版本

用{}占位符

		'hello, {}'.format('world')

用{index} index可以调换位置

		'hello, {0}, {1}'.format('world', 'python')

关键字参数 {argument}

		>>> 'hello, {world}, {python}'.format(world='world', python='python')'hello, world, python'

位置和关键字参数可任意组合

		'I\'m {0}, age {1}, come from {country}'.format('Lee', 19, country='China')>>> 'I\'m {0}, age {1}, come from {country}'.format('Lee', 19, country='China')"I'm Lee, age 19, come from China">>>

用**代表修饰字典参数

	>>> table{'a': 100, 'b': 200, 'c': 300}>>> 'a: {a}, b: {b}, c: {c}'.format(**table)'a: 100, b: 200, c: 300'>>>

用名称访问集合

>>> D = {'name': 'jack', 'age': 19, 'gender': 'male'}
>>> print('name: {[name]}'.format(D))
name: jack

练习

>>> for i in range(1, 11):
...     print(f'{i:2}, {i*i:3}, {i*i*i:4}') 
... 1,   1,    12,   4,    83,   9,   274,  16,   645,  25,  1256,  36,  2167,  49,  3438,  64,  5129,  81,  729
10, 100, 1000

4，手动格式字符串

# rjust(talbe_num) 用于相对位置空格>>> for x in range(1, 11):
...     print(repr(x).rjust(2), repr(x*x).rjust(3), repr(x*x*x).rjust(4)) 
... 1   1    12   4    83   9   274  16   645  25  1256  36  2167  49  3438  64  5129  81  729
10 100 1000