フォーマット済み文字列リテラル (f-strings)

>>> str_val = 'abc'
>>> f'{str_val:>6}'
'   abc'
 
>>> pi = 3.14159265358979
>>> f'pi: {pi:.2f}'
'pi: 3.14'
 
>>> f'pi: {pi:6.3f}'
'pi:  3.142'
 
>>> flt_val = 123456789.0123456
>>> f'float value: {flt_val:,.4f}'
'float value: 123,456,789.0123'
 
>>> flt_val = 1234.5678
>>> f'float value: {flt_val:>10,.2f}'
'float value:   1,234.57'
 
>>> f'float value: {flt_val:>14,.6f}'
'float value:   1,234.567800'
 
>>> 'int: {0:d}; hex: {0:#x}; oct: {0:#o}; bin: {0:#b}'.format(65536)
'int: 65536; hex: 0x10000; oct: 0o200000; bin: 0b10000000000000000'
 
>>> str = ' title '
>>> f'{str:->20}'
'------------- title '
>>> f'{str:-^20}'
'------ title -------'
>>> f'{str:-<20}'
' title -------------'
>>>

$ python
Python 3.8.3 (tags/v3.8.3:6f8c832, May 13 2020, 22:37:02) [MSC v.1924 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import timeit
>>> timeit.timeit("""name = "TomoYan";age = 99;
... f'{name} is {age}.'""", number = 1000000)
0.2775605999999584
>>> timeit.timeit("""name = "TomoYan";age = 99;
... '%s is %s.' % (name, age)""", number = 1000000)
0.36503240000001824
>>> timeit.timeit("""name = "TomoYan";age = 99;
... '{} is {}.'.format(name, age)""", number = 1000000)
0.4583815999999956
>>> timeit.timeit("""name = "TomoYan";age = 99;
... '{0} is {1}.'.format(name, age)""", number = 1000000)
>>>