Python - f string tricks

Sử dụng lại tên biến

str_value = "hello，python coders"
print(f"{ str_value = }")
# str_value = 'hello，python coders'

Thay đổi output

num_value = 125
print(f"{num_value % 2 = }")
# num_value % 2 = 1

Thay đổi date

import datetime

today = datetime.date.today()
print(f"{today: %Y%m%d}")
#20211224
print(f"{today =: %Y%m%d}")
#today = 20211224

Kiểu 2/8/16 Hexadecimal

>>> a = 42
>>> f"{a:b}"# Binary
'101010'
>>> f"{a:o}"# Octal
'52'
>>> f"{a:x}"# Hex, small letters
'2a'
>>> f"{a:X}"# Hex, capital letters
'2A'
>>> f"{a:c}"# ascii 码
'*'

Thay đổi Floating Point Number

>>> num_value = 223.456
>>> f'{num_value = :.2f}'
'num_value = 223.46'
>>> nested_format = ".2f"
>>> print(f'{num_value:{nested_format}}')
223.46

Kiểu chuỗi string

>>> x = 'test'
>>> f'{x:>10}'  # Right alignment
'      test'
>>> f'{x:*<10}' # Left alignment
'test******'
>>> f'{x:=^10}'# Center
'===test==='
>>> x, n = 'test', 10
>>> f'{x:~^{n}}'# Center
'~~~test~~~'

Thay đổi format

class MyClass:
    def __format__(self, format_spec) -> str:
        print(f'MyClass __format__ called with {format_spec!r}')
        return "MyClass()"

print(f'{MyClass():bala bala  %%MYFORMAT%%}')

# Output
MyClass __format__ called with format_spec='bala bala  %%MYFORMAT%%'
MyClass()

Special

>>> import timeit
>>> timeit.timeit("""name = "Tony"
        age = 100
        '%s is %s.' % (name, age)""", number = 10000)
# 0.0029884499333798885

>>> timeit.timeit("""name = "Tony"
        age = 100
        '{} is {}.'.format(name, age)""", number = 10000)
# 0.003444851143285632

>>> timeit.timeit("""name = "Tony"
        age = 100
        f'{name} is {age}.'""", number = 10000)
# 0.0018234248273074627