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IDLE in a Virtual Environment

3:23 with Kenneth Love

Using tools like IDLE in a virtualenv isn't as straightforward as it should be. I'll show you how to launch it so your custom project packages are available and how to use a requirements file to quickly build up an environment.

You can always get a list of installed packages with pip freeze. If you're in a virtualenv, you'll get the virtualenv's list of packages. If you're not, you'll get a list of your global packages. pip freeze > requirements.txt is the fast way to generate your requirements file the first time.

Requirements files always have the same layout: package_name==1.2.3. You can also use <, >, <= and >=, too (e.g. Django>=1.9,<2.0 would select the latest version of Django that's newer than, or equal to, 1.9 and less than 2.0).

  • 0:00

    Now, if you're going to use Idle and you're going to use virtualenv,

  • 0:03

    I need to show you a special thing for launching Idle inside of your virtualenv.

  • 0:09

    Normally, launching Idle would not let you use your virtualenv installed packages.

  • 0:14

    But if we launch Idle from inside of our virtualenv,

  • 0:19

    python -m idlelib, then we have access to our libraries.

  • 0:26

    Like here I can say import flasks, no problems.

  • 0:30

    So if your virtualenv gets screwed up and you need to start over, what do you do?

  • 0:35

    I said in the last video that they're disposable, right?

  • 0:38

    We deleted it, we made it again, and I mentioned installing packages.

  • 0:43

    So first of all, let's see what we have installed.

  • 0:45

    So we'll do pip freeze and we have flask, it's dangerous,

  • 0:50

    Jinja2,MarkupSafe and Werkzeug.

  • 0:53

    Which I apologize to all of my German speaking students.

  • 0:57

    I know I said that wrong.

  • 0:58

    If you can send me a better pronunciation of it, I would love it.

  • 1:01

    This givesa list of all the packages that we have installed and then we have this

  • 1:06

    double equals and the exact version of the package that we have installed,

  • 1:12

    so we have exactly Flask 0.10.1, not 0.10.2 or 0.10.0.

  • 1:18

    So we can copy this.

  • 1:21

    Alright, we can [SOUND] copy that.

  • 1:23

    Or we can be lazy.

  • 1:25

    We copy it, we paste it into a new file, right?

  • 1:27

    Or we can be lazy and let the computer do it for us.

  • 1:31

    So if we do pip freeze and then we do a greater than sign and

  • 1:34

    then the name of a file, which we're gonna do requirements.txt.

  • 1:40

    And now if I cat,

  • 1:42

    requirements requirements.txt which cat just makes it print.

  • 1:44

    It's got the same thing in there, so the greater than tells the computer to put

  • 1:49

    the output of pip freeze into a file named requirements.txt.

  • 1:53

    Now this file name isn't a requirement, but it is a very common practice to use

  • 1:58

    that name and some third parties services like Kiroku kind of expect that name.

  • 2:03

    Okay, so let's make sure this works.

  • 2:06

    So I should be able to get out of here, deactivate and

  • 2:10

    I should be able to rm -rf fb.

  • 2:13

    So I do not have fb installed.

  • 2:16

    And then, I should be able to make a new one.

  • 2:20

    So let's go up here, let's find my thing I did, there it is, python3 -m venv fb.

  • 2:27

    Alright and then, source fb/bin/activate.

  • 2:33

    Okay, we are back to this.

  • 2:34

    And if we do pip freeze, there is nothing installed yet

  • 2:37

    because I haven't installed things yet.

  • 2:39

    Let's install things.

  • 2:40

    So we can do pip install, and normally here we would type in like, flask, right?

  • 2:46

    Let's not do that, though.

  • 2:47

    -r says "Hey, go read this file".

  • 2:51

    And we're gonna read requirements.txt.

  • 2:54

    So press enter, and it installs everything.

  • 2:58

    And if we now do pip freeze, there is our normal list of all of our stuff.

  • 3:03

    Everything's installed again, that's awesome.

  • 3:07

    Congratulations, you have a solid local Python installation you can use to follow

  • 3:12

    along with the courses here on Treehouse or just for experimenting with code, or

  • 3:16

    writing software for clients of your own, or a developer job.

  • 3:20

    I'm sure you'll do so much with these new tools.

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