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default value & typing hint dataclasses
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‎README.md‎

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@@ -198,6 +198,8 @@ All contributions are welcome:
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- [setup.py](#setuppy)
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- [Dataclasses](#dataclasses)
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- [Features](#features)
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- [Default values](#default-values)
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- [Type hints](#type-hints)
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- [Virtual Environment](#virtual-environment)
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- [virtualenv](#virtualenv)
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- [pipenv](#pipenv)
@@ -539,26 +541,26 @@ The *and* Operator’s *Truth* Table:
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| Expression | Evaluates to |
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| ----------------- | ------------ |
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| `True and True` | `True` |
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| `True and False` | `False` |
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| `False and True` | `False` |
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| `False and False` | `False` |
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| `True and True` | `True` |
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| `True and False` | `False` |
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| `False and True` | `False` |
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| `False and False` | `False` |
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The *or* Operator’s *Truth* Table:
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| Expression | Evaluates to |
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| ---------------- | -------------- |
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| `True or True` | `True` |
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| `True or False` | `True` |
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| `False or True` | `True` |
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| `False or False` | `False` |
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| Expression | Evaluates to |
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| ---------------- | ------------ |
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| `True or True` | `True` |
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| `True or False` | `True` |
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| `False or True` | `True` |
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| `False or False` | `False` |
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The *not* Operator’s *Truth* Table:
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| Expression | Evaluates to |
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| ------------ | ------------- |
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| `not True` | `False` |
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| `not False` | `True` |
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| Expression | Evaluates to |
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| ----------- | ------------ |
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| `not True` | `False` |
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| `not False` | `True` |
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[*Return to the Top*](#python-cheatsheet)
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### Escape Characters
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| Escape character | Prints as |
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| ------------------ | -------------------- |
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| `\'` | Single quote |
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| `\"` | Double quote |
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| `\t` | Tab |
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| `\n` | Newline (line break) |
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| `\\` | Backslash |
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| Escape character | Prints as |
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| ---------------- | -------------------- |
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| `\'` | Single quote |
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| `\"` | Double quote |
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| `\t` | Tab |
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| `\n` | Newline (line break) |
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| `\\` | Backslash |
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Example:
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| `\d`, `\w`, and `\s` | a digit, word, or space character, ectively. |
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| `\D`, `\W`, and `\S` | anything except a digit, word, or space acter, respectively. |
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| `[abc]` | any character between the brackets (such as a, b, ). |
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| `[^abc]` | any character that isn’t between the brackets. |
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| `[^abc]` | any character that isn’t between the brackets. |
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[*Return to the Top*](#python-cheatsheet)
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| ---------- | -------------------- | ------------------------------------------------------------------------------------------------------------------------------ |
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| `DEBUG` | `logging.debug()` | The lowest level. Used for small details. Usually you care about these messages only when diagnosing problems. |
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| `INFO` | `logging.info()` | Used to record information on general events in your program or confirm that things are working at their point in the program. |
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| `WARNING` | `logging.warning()` | Used to indicate a potential problem that doesn’t prevent the program from working but might do so in the future. |
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| `WARNING` | `logging.warning()` | Used to indicate a potential problem that doesn’t prevent the program from working but might do so in the future. |
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| `ERROR` | `logging.error()` | Used to record an error that caused the program to fail to do something. |
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| `CRITICAL` | `logging.critical()` | The highest level. Used to indicate a fatal error that has caused or is about to cause the program to stop running entirely. |
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[*Return to the Top*](#python-cheatsheet)
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### Default values
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It is easy to add default values to the fields of your data class.
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```python
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>>> @dataclass
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... class Product:
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... name: str
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... count: int = 0
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... price: float = 0.0
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...
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>>> obj = Product("Python")
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>>> obj.name
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Python
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>>> obj.count
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0
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>>> obj.price
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0.0
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```
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### Type hints
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It is mandatory to define the data type in dataclass. However, If you don't want specify the datatype then, use ```typing.Any```.
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```python
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>>> from dataclasses import dataclass
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>>> from typing import Any
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>>> @dataclass
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... class WithoutExplicitTypes:
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... name: Any
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... value: Any = 42
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...
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```
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[*Return to the Top*](#python-cheatsheet)
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## Virtual Environment
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The use of a Virtual Environment is to test python code in encapsulated environments and to also avoid filling the base Python installation with libraries we might use for only one project.

‎blog_files/pysheet.md‎

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>>> obj.val
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2
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```
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### Default values
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It is easy to add default values to the fields of your data class.
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... name: Any
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... value: Any = 42
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...
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```
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```
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## Virtual Environment
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‎python_cheat_sheet.ipynb‎

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"- [setup.py](#setuppy)\n",
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"- [Dataclasses](#dataclasses)\n",
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" - [Features](#features)\n",
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" - [Default values](#default-values)\n",
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" - [Type hints](#type-hints)\n",
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"- [Virtual Environment](#virtual-environment)\n",
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" - [virtualenv](#virtualenv)\n",
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" - [pipenv](#pipenv)\n",
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"\n",
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"| Expression | Evaluates to |\n",
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"| ----------------- | ------------ |\n",
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"| `True and True` | `True` |\n",
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"| `True and False` | `False` |\n",
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"| `False and True` | `False` |\n",
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"| `False and False` | `False` |\n",
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"| `True and True` | `True` |\n",
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"| `True and False` | `False` |\n",
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"| `False and True` | `False` |\n",
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"| `False and False` | `False` |\n",
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"\n",
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"The *or* Operator’s *Truth* Table:\n",
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"\n",
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"| Expression | Evaluates to |\n",
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"| ---------------- | -------------- |\n",
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"| `True or True` | `True` |\n",
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"| `True or False` | `True` |\n",
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"| `False or True` | `True` |\n",
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"| `False or False` | `False` |\n",
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"| Expression | Evaluates to |\n",
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"| ---------------- | ------------ |\n",
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"| `True or True` | `True` |\n",
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"| `True or False` | `True` |\n",
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"| `False or True` | `True` |\n",
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"| `False or False` | `False` |\n",
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"\n",
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"The *not* Operator’s *Truth* Table:\n",
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"\n",
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"| Expression | Evaluates to |\n",
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"| ------------ | ------------- |\n",
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"| `not True` | `False` |\n",
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"| `not False` | `True` |\n",
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"| Expression | Evaluates to |\n",
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"| ----------- | ------------ |\n",
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"| `not True` | `False` |\n",
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"| `not False` | `True` |\n",
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"\n",
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"[*Return to the Top*](#python-cheatsheet)\n",
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"\n",
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"\n",
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"### Escape Characters\n",
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"\n",
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"| Escape character | Prints as |\n",
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"| ------------------ | -------------------- |\n",
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"| `\\'` | Single quote |\n",
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"| `\\\"` | Double quote |\n",
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"| `\\t` | Tab |\n",
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"| `\\n` | Newline (line break) |\n",
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"| `\\\\` | Backslash |\n",
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"| Escape character | Prints as |\n",
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"| ---------------- | -------------------- |\n",
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"| `\\'` | Single quote |\n",
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"| `\\\"` | Double quote |\n",
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"| `\\t` | Tab |\n",
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"| `\\n` | Newline (line break) |\n",
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"| `\\\\` | Backslash |\n",
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"\n",
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"Example:"
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]
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"| `\\d`, `\\w`, and `\\s` | a digit, word, or space character, ectively. |\n",
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"| `\\D`, `\\W`, and `\\S` | anything except a digit, word, or space acter, respectively. |\n",
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"| `[abc]` | any character between the brackets (such as a, b, ). |\n",
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"| `[^abc]` | any character that isn’t between the brackets. |\n",
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"| `[^abc]` | any character that isn’t between the brackets. |\n",
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"\n",
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"[*Return to the Top*](#python-cheatsheet)\n",
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"\n",
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"| ---------- | -------------------- | ------------------------------------------------------------------------------------------------------------------------------ |\n",
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"| `DEBUG` | `logging.debug()` | The lowest level. Used for small details. Usually you care about these messages only when diagnosing problems. |\n",
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"| `INFO` | `logging.info()` | Used to record information on general events in your program or confirm that things are working at their point in the program. |\n",
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"| `WARNING` | `logging.warning()` | Used to indicate a potential problem that doesn’t prevent the program from working but might do so in the future. |\n",
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"| `WARNING` | `logging.warning()` | Used to indicate a potential problem that doesn’t prevent the program from working but might do so in the future. |\n",
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"| `ERROR` | `logging.error()` | Used to record an error that caused the program to fail to do something. |\n",
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"| `CRITICAL` | `logging.critical()` | The highest level. Used to indicate a fatal error that has caused or is about to cause the program to stop running entirely. |\n",
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"\n",
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"2"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"[*Return to the Top*](#python-cheatsheet)\n",
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"\n",
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"### Default values\n",
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"\n",
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"It is easy to add default values to the fields of your data class."
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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">>> @dataclass\n",
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"... class Product:\n",
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"... name: str\n",
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"... count: int = 0\n",
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"... price: float = 0.0\n",
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"...\n",
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">>> obj = Product(\"Python\")\n",
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">>> obj.name\n",
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"Python\n",
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">>> obj.count\n",
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"0\n",
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">>> obj.price\n",
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"0.0"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"### Type hints\n",
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"\n",
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"It is mandatory to define the data type in dataclass. However, If you don't want specify the datatype then, use ```typing.Any```."
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {},
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"outputs": [],
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"source": [
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">>> from dataclasses import dataclass\n",
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">>> from typing import Any\n",
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"\n",
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">>> @dataclass\n",
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"... class WithoutExplicitTypes:\n",
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"... name: Any\n",
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"... value: Any = 42\n",
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"..."
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},

‎python_cheat_sheet.pdf‎

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