{"id":9633,"date":"2022-09-20T19:05:00","date_gmt":"2022-09-20T17:05:00","guid":{"rendered":"https:\/\/monodes.com\/predaelli\/?p=9633"},"modified":"2022-09-20T09:08:06","modified_gmt":"2022-09-20T07:08:06","slug":"9633","status":"publish","type":"post","link":"https:\/\/monodes.com\/predaelli\/2022\/09\/20\/9633\/","title":{"rendered":""},"content":{"rendered":"\n

Another interesting article to “convert to Eiffel”…. It’s Time to Say Goodbye to These Obsolete Python Libraries<\/a><\/p>\n\n\n

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It’s Time to Say Goodbye to These Obsolete Python Libraries<\/h1>\n
Martin<\/span>\n
<\/i>Python<\/a><\/div>\n<\/div>\n<\/header>\n
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With every Python release, there are new modules being added and new and better ways of doing things get introduced. We all get used to using the good old Python libraries and to certain way of doing things, but it’s time upgrade and make use of the new and improved modules and their features.<\/p>\n

Pathlib<\/h2>\n

pathlib<\/code> is definitely one of the bigger, recent additions to Python’s standard library. It’s been part of standard library since Python 3.4, yet a lot of people still use os<\/code> module for filesystem operations.<\/p>\n

pathlib<\/code> has however many advantages over old os.path<\/code> – while os<\/code> module represents paths in raw string format, pathlib<\/code> uses object-oriented style, which makes it more readable and natural to write:<\/p>\n

<span class="token keyword">from<\/span> pathlib <span class="token keyword">import<\/span> Path\n<span class="token keyword">import<\/span> os<span class="token punctuation">.<\/span>path\n\n<span class="token comment"># Old, Unreadable<\/span>\ntwo_dirs_up <span class="token operator">=<\/span> os<span class="token punctuation">.<\/span>path<span class="token punctuation">.<\/span>dirname<span class="token punctuation">(<\/span>os<span class="token punctuation">.<\/span>path<span class="token punctuation">.<\/span>dirname<span class="token punctuation">(<\/span>os<span class="token punctuation">.<\/span>path<span class="token punctuation">.<\/span>abspath<span class="token punctuation">(<\/span>__file__<span class="token punctuation">)<\/span><span class="token punctuation">)<\/span><span class="token punctuation">)<\/span>\n<span class="token comment"># New, Readable<\/span>\ntwo_dirs_up <span class="token operator">=<\/span> Path<span class="token punctuation">(<\/span>__file__<span class="token punctuation">)<\/span><span class="token punctuation">.<\/span>resolve<span class="token punctuation">(<\/span><span class="token punctuation">)<\/span><span class="token punctuation">.<\/span>parent<span class="token punctuation">.<\/span>parent<\/code><\/pre>\n
The fact that paths are treated as objects rather than strings also makes it possible to create the object once and then lookup its attributes or make operations on it:<\/p>\n
readme <span class="token operator">=<\/span> Path<span class="token punctuation">(<\/span><span class="token string">"README.md"<\/span><span class="token punctuation">)<\/span><span class="token punctuation">.<\/span>resolve<span class="token punctuation">(<\/span><span class="token punctuation">)<\/span>\n\n<span class="token keyword">print<\/span><span class="token punctuation">(<\/span><span class="token string-interpolation"><span class="token string">f"Absolute path: <\/span><span class="token interpolation"><span class="token punctuation">{<\/span>readme<span class="token punctuation">.<\/span>absolute<span class="token punctuation">(<\/span><span class="token punctuation">)<\/span><span class="token punctuation">}<\/span><\/span><span class="token string">"<\/span><\/span><span class="token punctuation">)<\/span>\n<span class="token comment"># Absolute path: \/home\/martin\/some\/path\/README.md<\/span>\n<span class="token keyword">print<\/span><span class="token punctuation">(<\/span><span class="token string-interpolation"><span class="token string">f"File name: <\/span><span class="token interpolation"><span class="token punctuation">{<\/span>readme<span class="token punctuation">.<\/span>name<span class="token punctuation">}<\/span><\/span><span class="token string">"<\/span><\/span><span class="token punctuation">)<\/span>\n<span class="token comment"># File name: README.md<\/span>\n<span class="token keyword">print<\/span><span class="token punctuation">(<\/span><span class="token string-interpolation"><span class="token string">f"Path root: <\/span><span class="token interpolation"><span class="token punctuation">{<\/span>readme<span class="token punctuation">.<\/span>root<span class="token punctuation">}<\/span><\/span><span class="token string">"<\/span><\/span><span class="token punctuation">)<\/span>\n<span class="token comment"># Path root: \/<\/span>\n<span class="token keyword">print<\/span><span class="token punctuation">(<\/span><span class="token string-interpolation"><span class="token string">f"Parent directory: <\/span><span class="token interpolation"><span class="token punctuation">{<\/span>readme<span class="token punctuation">.<\/span>parent<span class="token punctuation">}<\/span><\/span><span class="token string">"<\/span><\/span><span class="token punctuation">)<\/span>\n<span class="token comment"># Parent directory: \/home\/martin\/some\/path<\/span>\n<span class="token keyword">print<\/span><span class="token punctuation">(<\/span><span class="token string-interpolation"><span class="token string">f"File extension: <\/span><span class="token interpolation"><span class="token punctuation">{<\/span>readme<span class="token punctuation">.<\/span>suffix<span class="token punctuation">}<\/span><\/span><span class="token string">"<\/span><\/span><span class="token punctuation">)<\/span>\n<span class="token comment"># File extension: .md<\/span>\n<span class="token keyword">print<\/span><span class="token punctuation">(<\/span><span class="token string-interpolation"><span class="token string">f"Is it absolute: <\/span><span class="token interpolation"><span class="token punctuation">{<\/span>readme<span class="token punctuation">.<\/span>is_absolute<span class="token punctuation">(<\/span><span class="token punctuation">)<\/span><span class="token punctuation">}<\/span><\/span><span class="token string">"<\/span><\/span><span class="token punctuation">)<\/span>\n<span class="token comment"># Is it absolute: True<\/span><\/code><\/pre>\n
The one feature that I love the most about pathlib<\/code> though, is possibility to use the \/<\/code> (“division”<\/i>) operator to join paths:<\/p>\n
<span class="token comment"># Operators:<\/span>\netc <span class="token operator">=<\/span> Path<span class="token punctuation">(<\/span><span class="token string">'\/etc'<\/span><span class="token punctuation">)<\/span>\n\njoined <span class="token operator">=<\/span> etc <span class="token operator">\/<\/span> <span class="token string">"cron.d"<\/span> <span class="token operator">\/<\/span> <span class="token string">"anacron"<\/span>\n<span class="token keyword">print<\/span><span class="token punctuation">(<\/span><span class="token string-interpolation"><span class="token string">f"Exists? - <\/span><span class="token interpolation"><span class="token punctuation">{<\/span>joined<span class="token punctuation">.<\/span>exists<span class="token punctuation">(<\/span><span class="token punctuation">)<\/span><span class="token punctuation">}<\/span><\/span><span class="token string">"<\/span><\/span><span class="token punctuation">)<\/span>\n<span class="token comment"># Exists? - True<\/span><\/code><\/pre>\n
This makes handling of paths so easy and really is a chef\u2019s kiss<\/i> \ud83d\udc4c.<\/p>\n
With that said, it’s important to note that pathlib<\/code> is only replacement for os.path<\/code> and not a whole os<\/code> module. It however includes also functionality from glob<\/code> module, so if you’re used to using os.path<\/code> in combination with glob.glob<\/code>, then you can just forget that those 2 exist.<\/p>\n
In the above snippets we presented some handy path manipulations and object attributes, but pathlib<\/code> also includes all the methods that you’re used to from os.path<\/code>, such as:<\/p>\n
<span class="token keyword">print<\/span><span class="token punctuation">(<\/span><span class="token string-interpolation"><span class="token string">f"Working directory: <\/span><span class="token interpolation"><span class="token punctuation">{<\/span>Path<span class="token punctuation">.<\/span>cwd<span class="token punctuation">(<\/span><span class="token punctuation">)<\/span><span class="token punctuation">}<\/span><\/span><span class="token string">"<\/span><\/span><span class="token punctuation">)<\/span>  <span class="token comment"># same as os.getcwd()<\/span>\n<span class="token comment"># Working directory: \/home\/martin\/some\/path<\/span>\nPath<span class="token punctuation">.<\/span>mkdir<span class="token punctuation">(<\/span>Path<span class="token punctuation">.<\/span>cwd<span class="token punctuation">(<\/span><span class="token punctuation">)<\/span> <span class="token operator">\/<\/span> <span class="token string">"new_dir"<\/span><span class="token punctuation">,<\/span> exist_ok<span class="token operator">=<\/span><span class="token boolean">True<\/span><span class="token punctuation">)<\/span>  <span class="token comment"># same as os.makedirs()<\/span>\n<span class="token keyword">print<\/span><span class="token punctuation">(<\/span>Path<span class="token punctuation">(<\/span><span class="token string">"README.md"<\/span><span class="token punctuation">)<\/span><span class="token punctuation">.<\/span>resolve<span class="token punctuation">(<\/span><span class="token punctuation">)<\/span><span class="token punctuation">)<\/span>  <span class="token comment"># same as os.path.abspath()<\/span>\n<span class="token comment"># \/home\/martin\/some\/path\/README.md<\/span>\n<span class="token keyword">print<\/span><span class="token punctuation">(<\/span>Path<span class="token punctuation">.<\/span>home<span class="token punctuation">(<\/span><span class="token punctuation">)<\/span><span class="token punctuation">)<\/span>  <span class="token comment"># same as os.path.expanduser()<\/span>\n<span class="token comment"># \/home\/martin<\/span><\/code><\/pre>\n
For full mapping of os.path<\/code> functions to new ones in pathlib<\/code> see docs<\/a> .<\/p>\n
For more examples of how great pathlib<\/code> is, check out nice write-up by Trey Hunner<\/a>.<\/p>\n
Secrets<\/h2>\n
Speaking of os<\/code> module, another part of it that you should stop using is os.urandom<\/code>. Instead, you should use new secrets<\/code> module available since Python 3.6:<\/p>\n
<span class="token comment"># Old:<\/span>\n<span class="token keyword">import<\/span> os\n\nlength <span class="token operator">=<\/span> <span class="token number">64<\/span>\n\nvalue <span class="token operator">=<\/span> os<span class="token punctuation">.<\/span>urandom<span class="token punctuation">(<\/span>length<span class="token punctuation">)<\/span>\n<span class="token keyword">print<\/span><span class="token punctuation">(<\/span><span class="token string-interpolation"><span class="token string">f"Bytes: <\/span><span class="token interpolation"><span class="token punctuation">{<\/span>value<span class="token punctuation">}<\/span><\/span><span class="token string">"<\/span><\/span><span class="token punctuation">)<\/span>\n<span class="token comment"># Bytes: b'\\xfa\\xf3...\\xf2\\x1b\\xf5\\xb6'<\/span>\n<span class="token keyword">print<\/span><span class="token punctuation">(<\/span><span class="token string-interpolation"><span class="token string">f"Hex: <\/span><span class="token interpolation"><span class="token punctuation">{<\/span>value<span class="token punctuation">.<\/span><span class="token builtin">hex<\/span><span class="token punctuation">(<\/span><span class="token punctuation">)<\/span><span class="token punctuation">}<\/span><\/span><span class="token string">"<\/span><\/span><span class="token punctuation">)<\/span>\n<span class="token comment"># Hex: faf3cc656370e31a938e7...33d9b023c3c24f1bf5<\/span>\n\n<span class="token comment"># New:<\/span>\n<span class="token keyword">import<\/span> secrets\n\nvalue <span class="token operator">=<\/span> secrets<span class="token punctuation">.<\/span>token_bytes<span class="token punctuation">(<\/span>length<span class="token punctuation">)<\/span>\n<span class="token keyword">print<\/span><span class="token punctuation">(<\/span><span class="token string-interpolation"><span class="token string">f"Bytes: <\/span><span class="token interpolation"><span class="token punctuation">{<\/span>value<span class="token punctuation">}<\/span><\/span><span class="token string">"<\/span><\/span><span class="token punctuation">)<\/span>\n<span class="token comment"># Bytes: b'U\\xe9n\\x87...\\x85>\\x04j:\\xb0'<\/span>\nvalue <span class="token operator">=<\/span> secrets<span class="token punctuation">.<\/span>token_hex<span class="token punctuation">(<\/span>length<span class="token punctuation">)<\/span>\n<span class="token keyword">print<\/span><span class="token punctuation">(<\/span><span class="token string-interpolation"><span class="token string">f"Hex: <\/span><span class="token interpolation"><span class="token punctuation">{<\/span>value<span class="token punctuation">}<\/span><\/span><span class="token string">"<\/span><\/span><span class="token punctuation">)<\/span>\n<span class="token comment"># Hex: fb5dd85e7d73f7a08b8e3...4fd9f95beb08d77391<\/span><\/code><\/pre>\n
Using os.urandom<\/code> isn’t actually the problem here though, the reason<\/a> secrets<\/code> module got introduced is because people were using random<\/code> module for generating passwords and such, even though random<\/code> module doesn’t produce cryptographically safe tokens.<\/p>\n
As per docs, random<\/code> module should not be used for security purposes. You should use either secrets<\/code> or os.urandom<\/code>, but the secrets<\/code> module is definitely preferable, considering that it’s newer and includes some utility\/convenience methods for hexadecimal tokens as well as URL safe tokens.<\/p>\n
Zoneinfo<\/h2>\n
Until Python 3.9, there wasn’t builtin library for timezone manipulation, so everyone was using pytz<\/code>, but now we have zoneinfo<\/code> in standard library, so it’s time to switch!<\/p>\n
<span class="token keyword">from<\/span> datetime <span class="token keyword">import<\/span> datetime\n<span class="token keyword">import<\/span> pytz  <span class="token comment"># pip install pytz<\/span>\n\ndt <span class="token operator">=<\/span> datetime<span class="token punctuation">(<\/span><span class="token number">2022<\/span><span class="token punctuation">,<\/span> <span class="token number">6<\/span><span class="token punctuation">,<\/span> <span class="token number">4<\/span><span class="token punctuation">)<\/span>\nnyc <span class="token operator">=<\/span> pytz<span class="token punctuation">.<\/span>timezone<span class="token punctuation">(<\/span><span class="token string">"America\/New_York"<\/span><span class="token punctuation">)<\/span>\n\nlocalized <span class="token operator">=<\/span> nyc<span class="token punctuation">.<\/span>localize<span class="token punctuation">(<\/span>dt<span class="token punctuation">)<\/span>\n<span class="token keyword">print<\/span><span class="token punctuation">(<\/span><span class="token string-interpolation"><span class="token string">f"Datetime: <\/span><span class="token interpolation"><span class="token punctuation">{<\/span>localized<span class="token punctuation">}<\/span><\/span><span class="token string">, Timezone: <\/span><span class="token interpolation"><span class="token punctuation">{<\/span>localized<span class="token punctuation">.<\/span>tzname<span class="token punctuation">(<\/span><span class="token punctuation">)<\/span><span class="token punctuation">}<\/span><\/span><span class="token string">, TZ Info: <\/span><span class="token interpolation"><span class="token punctuation">{<\/span>localized<span class="token punctuation">.<\/span>tzinfo<span class="token punctuation">}<\/span><\/span><span class="token string">"<\/span><\/span><span class="token punctuation">)<\/span>\n\n<span class="token comment"># New:<\/span>\n<span class="token keyword">from<\/span> zoneinfo <span class="token keyword">import<\/span> ZoneInfo\n\nnyc <span class="token operator">=<\/span> ZoneInfo<span class="token punctuation">(<\/span><span class="token string">"America\/New_York"<\/span><span class="token punctuation">)<\/span>\nlocalized <span class="token operator">=<\/span> datetime<span class="token punctuation">(<\/span><span class="token number">2022<\/span><span class="token punctuation">,<\/span> <span class="token number">6<\/span><span class="token punctuation">,<\/span> <span class="token number">4<\/span><span class="token punctuation">,<\/span> tzinfo<span class="token operator">=<\/span>nyc<span class="token punctuation">)<\/span>\n<span class="token keyword">print<\/span><span class="token punctuation">(<\/span><span class="token string-interpolation"><span class="token string">f"Datetime: <\/span><span class="token interpolation"><span class="token punctuation">{<\/span>localized<span class="token punctuation">}<\/span><\/span><span class="token string">, Timezone: <\/span><span class="token interpolation"><span class="token punctuation">{<\/span>localized<span class="token punctuation">.<\/span>tzname<span class="token punctuation">(<\/span><span class="token punctuation">)<\/span><span class="token punctuation">}<\/span><\/span><span class="token string">, TZ Info: <\/span><span class="token interpolation"><span class="token punctuation">{<\/span>localized<span class="token punctuation">.<\/span>tzinfo<span class="token punctuation">}<\/span><\/span><span class="token string">"<\/span><\/span><span class="token punctuation">)<\/span>\n<span class="token comment"># Datetime: 2022-06-04 00:00:00-04:00, Timezone: EDT, TZ Info: America\/New_York<\/span><\/code><\/pre>\n
The datetime<\/code> module delegates all timezone manipulation to abstract base class datetime.tzinfo<\/code>. This abstract base class needs a concrete implementation – before introducing this module that would most likely come from pytz<\/code>. Now that we have zoneinfo<\/code> in standard library we can use that instead.<\/p>\n
Using zoneinfo<\/code> however has one caveat – it assumes that there’s time zone data available on the system, which is the case on UNIX systems. If your system doesn’t have timezone data though, then you should use tzdata<\/a> package which is a first-party library maintained by the CPython core developers, which contains IANA time zone database.<\/p>\n
Dataclasses<\/h2>\n
An important addition to Python 3.7 was dataclasses<\/code> package which is a replacement for namedtuple<\/code>.<\/p>\n
You might be wondering why would you need to replace namedtuple<\/code>? So, these are some reasons why you should consider switching to dataclasses<\/code>:<\/p>\n