独家 | Python 3.10发布——你应该知道的五大新特性

# I am coding in Python and this is first line ;)
my_list = ["Hello", "Python!"
print(my_list)

File "my_precious.py", line 3
    print(my_list)
        ^
SyntaxError: invalid syntax

File "my_precious.py", line 2
    news = ["Hello", "Python!"
           ^
SyntaxError: '[' was never closed

# missing_comma.py


dc_characters = {
    1: "Superman"       # Comma missing
    2: "Batman",
    3: "Joker"
}


....
Output:
File "dc_characters.py", line 4
    10: "October"
        ^^^^^^^^^
SyntaxError: invalid syntax. Perhaps you forgot a comma?

# Before Python 3.10 Release
from typing import Union
def f(list: List[Union[int, str]], param: Optional[int]):
    pass


# In Python 3.10 Release
def f(list: List[int | str], param: int | None):
    pass


# Calling the function
f([1, “abc”], None)

int | str == typing.Union[int, str]


typing.Union[int, int] == int
int | int == int

# Before Python 3.10 Release


with (open("a_really_long_foo") as foo,
      open("a_really_long_bar") as bar):
    pass


Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "demo.py", line 19
    with (open("a_really_long_foo") as foo,
                                    ^
SyntaxError: invalid syntax

# After Python 3.10 Release


from contextlib import contextmanager


@contextmanager
def f(x):
    try:
        yield x
    finally:
        pass


# Example 1
with f('c') as a,
     f('a') as b:
     pass


# Example 2
with f('c') as a,
     f('a') as b,
     f('a') as c:
     pass

# Before Python 3.10
UserInfo = tuple[str, int]

# In Python 3.10


from typing import TypeAlias


Card: TypeAlias = tuple[str, str]
Deck: TypeAlias = list[Card]

# Before Python 3.10
names = ["Tom", "Harry", "Jessica", "Robert", "Kevin"]
numbers = ["21024", "75978", "92176", "75192", "34323"]

list(zip(names, numbers))


.....
Output:
[(Tom, 21024), (Harry, 75978), (Jessica, 92176), (Robert, 75192), (Kevin, 34323)]

# Before Python 3.10
names = ["Tom", "Harry", "Jessica", "Robert"]     # Kevin is missing
numbers = ["21024", "75978", "92176", "75192", "34323"]


# Zipping using zip()
list(zip(names, numbers))


......
Output
[(Tom, 21024), (Harry, 75978), (Jessica, 92176), (Robert, 75192)]

# In Python 3.10
names = ["Tom", "Harry", "Jessica", "Robert"]     # Kevin is missing
numbers = ["21024", "75978", "92176", "75192", "34323"]# Zipping using zip() with additional Parameter strict=True
list(zip(names, numbers, strict=True))....
Output:
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: zip() argument 2 is shorter than argument 1