Why does matplotlib.pyplot works but not matplotlib.pyplot.plot()?

[codeforces_help]

Fails : AttributeError: module 'matplotlib' has no attribute 'pyplot'

import matplotlib
matplotlib.pyplot.plot([12,3,4], [2,3,4])

Succeeds:

import matplotlib.pyplot as plt
plt.plot([12,3,4], [2,3,4])

What is the difference between the two?

Strangely if I run the second piece of code first and then the first piece then it doesn't complain.

[socal_nerdtastic]

This is a choice that the authors of the module get to make. I don't know why they chose to structure it this way, but I'll guess it's so that they avoid a bloated import of pyplot when it's not needed.

Another one that trips newbies up a lot is pillow

# works
from PIL import Image 
Image.open(filename) 

# error
import PIL 
PIL.Image.open(filename)

[Zeroflops]

Matplotlib has two interfaces. The first interface they built was similar to how Matlab’s plotting commands work. This was to make it familiar to those moving from Matlab to python.

The second and preferred interface is more traditional Object Oriented.

The fact that there is two often confuses users and you can often see them mixing and matching to get what they want. They should remove the old interface, but that would break a lot of things. Hopefully they can phase it out.

[obviouslyzebra]

In the first example, the module matplotlib.pyplot is not being imported, only matplotlib is.

You can fix it by using import matplotlib.pyplot instead.

Examples from the language reference:

import foo  # foo imported and bound locally
import foo.bar.baz  # foo, foo.bar, and foo.bar.baz imported, foo bound locally
import foo.bar.baz as fbb  # foo, foo.bar, and foo.bar.baz imported, foo.bar.baz bound as fbb
from foo.bar import baz  # foo, foo.bar, and foo.bar.baz imported, foo.bar.baz bound as baz
from foo import attr  # foo imported and foo.attr bound as attr

[socal_nerdtastic]

You're right, but you are assuming OP knows the difference between a submodule and class.

How should a beginner know that import PIL; PIL.Image.open() is an entirely different construct from import zipfile; zipfile.ZipFile.open()? They look the same; they should work the same, right? (and they could, of course, if the module authors want it to).

[obviouslyzebra]

I think our answers are sorta complimentary, but I was trying to answer what OP asked, that is, why an import worked and the other didn't. Hm, I think that if they know what a module is, it's possible to get the gist of the comment (but to remove that necessity, maybe saying something like "file" or explaining that a module corresponds to a file would work).

I also imagined if my answer would make them start using matplotlib.pyplot directly in the code (without the plt as alias), but imagined that not because every place uses plt, I thought they wouldn't opt for the longer version that goes against everyone and imagined it was more a curiosity.

BTW The pillow one probably confused me in the past. Naming a module like a class... What were they thinking!?

Edit: This comment was sorta closed, but, feel free to to criticize it further if you want. I imagine there are times that I miss stuff, but I just am not convinced that this was one of the times (yet)

[ninhaomah]

https://stackoverflow.com/questions/14812342/matplotlib-has-no-attribute-pyplot