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[Python Tips] Type Annotation by themarkymark

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[Python Tips] Type Annotation
![](https://steemitimages.com/DQmSsFP8BDE1DkXNN9hh1729MRexyqupLEKfWJTsRskjt33/image.png)

Python is a dynamic language that does not require you to specify data types as you create variables or supply return types.  This makes development a lot easier but can introduce unexpected bugs when things don't go as expected.

Typed languages help prevent bugs by making sure **strings** are strings, and *ints* are ints when they need to be.  This can save hours of debugging when suddenly something doesn't work when it used to in the past.

While Python doesn't require types, 3.5 added the option to specify a type.  This allows Python IDE's like PyCharm and linters to provide better insight into your code and warn you of type misusage.

While the syntax in Python 3.5 works, it depended on comments which don't always display properly in different editors for this sort of thing.  3.6 took it further and added a specific syntax that displays better in editors that support it.

I will not cover the 3.5 Syntax as you should be using 3.6 if you are using Python 3.

# Type Annotation in Python 3.6

In 3.5 you could type hint lists and dicts and this hasn't changed in 3.6.

### No type hinting

```
employees = []

```

### Type hinting

``` 
employees  = List[str]
```

The type hinting specifies a list of strings.  Now nothing will stop you from putting an int or a float in there, everything will work perfectly fine but if your business logic expects strings and gets a float your code may break without any previous warning.

Using an IDE like PyCharms would have warned you that there was a float in your list of strings.  You can also use mypy type checker or any number of code linters.

All the above code is compatible with 3.5,  when we start dealing with variables that are not strings or dicts is when the syntax changes between 3.5 and 3.6.    The below code only works with 3.6.

### No type checking

`employee = 'Bob'`

### Type checking

`employee : str = 'Bob'`

While this seems like a simple change, it can prove extremely useful when your code suddenly breaks for no apparent reason.

The syntax is simple

`variable : [TYPE] = [VALUE]`

The only change is adding a : and a [TYPE] to your variable declarations.  You can verify the type with type().   If you are not using a code linter, I highly suggest you do.  I will cover linting in a future post.




# My Python Tips Series
* [f-strings in Python 3.6](https://steemit.com/programming/@themarkymark/python-tips-f-strings-in-python-3-6-and-why-you-should-be-using-them)
* [Underscores in numeric literals](https://steemit.com/programming/@themarkymark/python-tips-underscores-in-numeric-literals)
* [A better interactive shell](https://steemit.com/programming/@themarkymark/python-tips-a-better-interactive-shell)
* [Secrets Module - New in 3.6](https://steemit.com/programming/@themarkymark/python-tips-secrets-module-new-in-3-6)
* [PEP 8](https://steemit.com/programming/@themarkymark/python-tips-pep-8)
* [Slices](https://steemit.com/programming/@themarkymark/python-tips-slices)
* [Named Tuples](https://steemit.com/programming/@themarkymark/python-tips-named-tuples)
* [Destructuring](https://steemit.com/programming/@themarkymark/python-tips-destructuring)
* [Counter](https://steemit.com/programming/@themarkymark/python-tips-counter)
👍  , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , and 132 others
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vote details (196)
@ahmedibrahem · 
Yes, we welcome such programs that serve many colleagues and friends
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@doryumira · 
Ohhh okay cool this is good, I'm a Python n00b so I had no idea about the difference in syntax between 3.5 and 3.6. 

I was using Intellij for awhile but I think I broke it and somehow Pycharm was giving me issues as well so now I just use IDLE and so far it's been pretty great. 

I tried rocking your example in that and it worked perfectly 
(well, except for the missing  = after str heh 😅 ):

![TypeAnnotation.JPG](https://steemitimages.com/DQmZx5ogJsQsLY7PrfRMi7Q2n9gVMw8rPcPiMdZ2b1rXxJK/TypeAnnotation.JPG)

Thanks for posting this, @themarkymark! 
Will work my way through the rest 👍
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@epearson · 
Cool series you have here. Are you going to do any tutorials on DTube?
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@izge · 
To be candid, the more i read more my head goes into the jungle. I thought you were talking about the snake python that we all know until i started reading programming. 😯
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@lamkote · 
Hi @themarkymark. I've choice you as one of my witness vote
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@themarkymark · 
Thanks :)
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@linnyplant · 
Woke up, looked at steemit feed....did not expect to see a post on python.  Not a developer and the time I last used that language was in Uni.  :) Anyway, your post made me wonder why I wanted to relearn a while ago, because I had a friend who kept insisting I should learn ruby instead.  I’ve only ever needed to use JavaScript for work.  Anyway, no time for learning a new coding language atm, but nice little reminder.
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@piscaryk · 
If you already know one language, other will not be as hard to learn.
That said, classical JavaScript is used in the browser and therefore a little different in its usage. Python, Ruby and JavaScript on Node are pretty similar though.

Not having time is a bad excuse. "Translate" one concept you know from one language to another each week and you will be a pro in no time ;)
👍  
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@linnyplant ·
$0.05
‘Time’ is a valid excuse.  My days are filled with configuring software and current system does not need me to customise existing JavaScript anymore.  I’d need an excuse to learn Python.  It’s been on the back of my mind it’s a useful language for years, but current interests that take my free time is writing.  Maybe when I give myself a programming challenge, I’ll look into the Steemit development side of things as a different focus.  That interests me, but I just need <i>time</i>. 

Thank you for the encouragement though. :)
👍  
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vote details (1)
@lovelyworld · 
A most perfect idea @themarkymark

A meaningful learning in doing pemogramman Something that can ease to accelerate the activities we do in terms of typing using Python is easy for us to do our activities.
Thank's @themarkymark it important step
<hr>
https://steemitimages.com/DQmWVTd56QaVvrwMGQLXdZAv66VGdhTeKvBQLMkLYJNk3q2/imageedit_10_7647874724.gif
<hr>
👍  
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@makerhacks · 
Ooh, I like it. Coming from strongly typed languages, it has been a debugging worry of mine :)
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@nathen007 · (edited)
mate, apologies for hijacking another of your incredible posts about snakes, but as the no.1 abuse blocker here, could I just draw your attention to this screenshot please. Perhaps you might like to investigate further via his blog shown on the pic...this is the 4th or 5th time hes bought a lot of accounts this way.
![Screenshot_71.png](https://steemitimages.com/DQmNpZq769SjoHUtBURStGgonMd22rZbqUHS3ZXrULrGQrq/Screenshot_71.png)
The site is microworkers and there is more and more of this shit going on there including circle jerking circles and paid for upvotes to win competitions etc.
👍  
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@qurator-tier-0 · 
<div class="pull-left"><img src="![Qsmall.png](https://steemitimages.com/DQmcWoZUnPrRW1UdZeVPWhHpnXfkgWAdFHGxMrSgZoxSZw8/Qsmall.png)" /></div>
		
<center>You just received a Tier 0 upvote!  Looking for bigger rewards? Click [here](https://steemit.com/qurator/@qurator/qurator-tier-changes) and learn how to get them or visit us on [Discord](https://discord.gg/nhQehdv)</center>
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@techstack · (edited)
Good to know about those annotation. Thanks for sharing. If you have some time then please take a look to my open source app I made for Steemit’s user. It’s about steemit recent posts feed widget.
[Steemit recent post widget](https://steemit.com/steemit/@techstack/improvisation-of-my-steemit-recent-posts-app-widget)
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@transparencybot · (edited)
<h3>This post has received votes totaling more than $50.00 from the following pay for vote services:</h3>

minnowbooster upvote in the amount of $84.65 STU, $166.77 USD.

**For a total calculated value of $85 [STU,](http://steem.supply/rewards) $167 USD before curation, with approx. $21 USD curation being earned by the paid voters.**

This information is being presented in the interest of transparency on our platform @themarkymark **and is by no means a judgement of your work.**
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@tyramisoux · (edited)
I do "C" and Assembler but really fight with this high-level languages.
There also too much changes with the different versions which really sucks.
Maybe I finally get used to it now using "beem" library. This stuff force me using python.
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@xpressng ·
$0.71
Wow! This looks amazing but I'm confused. As much as i like programming, i feel the process is really strenous. 

I like that all the codes put together just form an awesome outcome.

LInes like this 

> Python IDE's like PyChar 

Just made me more confused😭😭 this is not for me. Kudos to programmers. Y'all deserve some accolade
👍  
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root_title"[Python Tips] Type Annotation"
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