Python F-Strings (Since Python 3.6+)

>>> f'{12345:+}'      # [sign] (+/-)
'+12345'
>>> f'{-12345:+}'
'-12345'
>>> f'{-12345:+10}'
' -12345'
>>> f'{-12345:+010}'
'-000012345'

>>> f'{-12345:0=10}'  # negative numbers
'-000012345'
>>> f'{12345:010}'    # [0] shortcut (no align)
'0000012345'
>>> f'{-12345:010}'
'-000012345'
>>> import math       # [.precision]
>>> math.pi
3.141592653589793
>>> f'{math.pi:.2f}'
'3.14'
>>> f'{1000000:,.2f}' # [grouping\_option]
'1,000,000.00'
>>> f'{1000000:\_.2f}'
'1\_000\_000.00'
>>> f'{0.25:0%}'      # percentage
'25.000000%'
>>> f'{0.25:.0%}'
'25%'

>>> f'{10:b}'        # binary type
'1010'
>>> f'{10:o}'        # octal type
'12'
>>> f'{200:x}'       # hexadecimal type
'c8'
>>> f'{200:X}'
'C8'
>>> f'{345600000000:e}' # scientific notation
'3.456000e+11'
>>> f'{65:c}'       # character type
'A'
>>> f'{10:#b}'      # [type] with notation (base)
'0b1010'
>>> f'{10:#o}'
'0o12'
>>> f'{10:#x}'
'0xa'

>>> f'{"text":10}'     # [width]
'text '
>>> f'{"test":\*>10}'   # fill left
'\*\*\*\*\*\*test'
>>> f'{"test":\*<10}'   # fill right
'test\*\*\*\*\*\*'
>>> f'{"test":\*^10}'   # fill center
'\*\*\*test\*\*\*'
>>> f'{12345:0>10}'    # fill with numbers
'0000012345'

>>> website = 'Quickref.ME'
>>> f"Hello, {website}"
"Hello, Quickref.ME"
>>> num = 10
>>> f'{num} + 10 = {num + 10}'
'10 + 10 = 20'
>>> f"""He said {"I'm John"}"""
"He said I'm John"
>>> f'5 {"{stars}"}'
'5 {stars}'
>>> f'{{5}} {"stars"}'
'{5} stars'
>>> name = 'Eric'
>>> age = 27
>>> f"""Hello!
...  I'm {name}.
...  I'm {age}."""
"Hello!\n I'm Eric.\n I'm 27."

it is available since Python 3.6, also see: Formatted string literals