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Python

Python#

Sort Tuple List#

tup_list.sort(key=lambda tup: tup[0])

Iterate with Index#

for i, v in enumerate(arr):
    pass

Python in One Line#

List comprehension:

[expression for item in list]

Dict comprehension:

{key: value for vars in iterable}

Labmda:

x = lambda a, b : a * b

Clone Object#

Create object and copy attributes:

dst = src.__class__.__new__(src.__class__)
dst.__dict__.update(src.__dict__)

Deep Copy:

copy.deepcopy()

Basic Type Casting/Conversion#

String to bytes:

'str'.encode()

Bytes to string:

b'bytes'.decode('utf8')

Hex string to bytes:

bytes.fromhex('dead')

Dict to tuple list:

dict.items()

List to set:

set([1, 1, 1])

Class#

Pass all arguments to parent constructor in child class:

def __init__(self, *args, **kwargs):
    super().__init__(*args, **kwargs)

Use class as plain old data structure (POD) via dataclasses [1]:

from dataclasses import dataclass

@dataclass
class InventoryItem:
    """Class for keeping track of an item in inventory."""
    name: str
    unit_price: float
    quantity_on_hand: int = 0

    def total_cost(self) -> float:
        return self.unit_price * self.quantity_on_hand

# Constructor will be automatically generated::

def __init__(self, name: str, unit_price: float, quantity_on_hand: int=0):
    self.name = name
    self.unit_price = unit_price
    self.quantity_on_hand = quantity_on_hand

备注

New in python 3.7.

Auto Enumerations like iota in golang:

from enum import Enum, auto
class Color(Enum):
    RED = auto()
    GREEN = auto()
    BLUE = auto()

File Operations#

Temp file with real path:

f = tempfile.NamedTemporaryFile()
f.name

Temp directory:

tempfile.mkdtemp(prefix='blahblah')

Delete directory:

shutil.rmtree(dir)

Get basename:

os.path.basename()

Get extname:

fn, ext = os.path.splitext(fn)

Create soft/symbolic link:

os.symlink(src, dst)

Packing#

Check pypi upload error:

$ twine check dist/*

Check source and wheel content:

$ tar tf dist/*.tar.gz
$ unzip -l dist/*.whl
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