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Difference between data type ‘datetime64[ns]’ and ‘

datetime64[ns] is a general dtype, while <M8[ns] is a specific dtype. General dtypes map to specific dtypes, but may be different from one installation of NumPy to the next. On a machine whose byte order is little endian, there is no difference between np.dtype(‘datetime64[ns]’) and np.dtype(‘<M8[ns]’): However, on a big endian machine, np.dtype(‘datetime64[ns]’) would equal np.dtype(‘>M8[ns]’). So datetime64[ns] maps to either <M8[ns] or >M8[ns] depending on the endian-ness of the … Read more

What should I use to open a url instead of urlopen in urllib3

I wanted to write a piece of code like the following: But I found that I have to install urllib3 package now. Moreover, I couldn’t find any tutorial or example to understand how to rewrite the above code, for example, urllib3 does not have urlopen. Any explanation or example, please?! P/S: I’m using python 3.4.

Is there a head and tail method for Numpy array?

I loaded a csv file into ‘dataset’ and tried to execute dataset.head(), but it reports an error. How to check the head or tail of a numpy array? without specifying specific lines?

How to check if a user is logged in (how to properly use user.is_authenticated)?

Update for Django 1.10+: is_authenticated is now an attribute in Django 1.10. The method was removed in Django 2.0. For Django 1.9 and older: is_authenticated is a function. You should call it like As Peter Rowell pointed out, what may be tripping you up is that in the default Django template language, you don’t tack … Read more

Must have equal len keys and value when setting with an iterable

You can use apply to index into leader and exchange values with DatasetLabel, although it’s not very pretty. One issue is that Pandas won’t let us index with NaN. Converting to str provides a workaround. But that creates a second issue, namely, column 9 is of type float (because NaN is float), so 5 becomes … Read more

Can’t concat bytes to str

subprocess.check_output() returns a bytestring. In Python 3, there’s no implicit conversion between unicode (str) objects and bytes objects. If you know the encoding of the output, you can .decode() it to get a string, or you can turn the \n you want to add to bytes with “\n”.encode(‘ascii’)

numpy array concatenation error: 0-d arrays can’t be concatenated

You need to put the arrays you want to concatenate into a sequence (usually a tuple or list) in the argument. Check the documentation for np.concatenate. Note that the first argument is a sequence (e.g. list, tuple) of arrays. It does not take them as separate arguments. As far as I know, this API is … Read more

In Python, how do I determine if an object is iterable?

Checking for __iter__ works on sequence types, but it would fail on e.g. strings in Python 2. I would like to know the right answer too, until then, here is one possibility (which would work on strings, too): from __future__ import print_function try: some_object_iterator = iter(some_object) except TypeError as te: print(some_object, ‘is not iterable’) The … Read more

Numpy Resize/Rescale Image

Yeah, you can install opencv (this is a library used for image processing, and computer vision), and use the cv2.resize function. And for instance use: Here img is thus a numpy array containing the original image, whereas res is a numpy array containing the resized image. An important aspect is the interpolation parameter: there are … Read more

Python: Convert timedelta to int in a dataframe

I would like to create a column in a pandas data frame that is an integer representation of the number of days in a timedelta column. Is it possible to use ‘datetime.days’ or do I need to do something more manual? timedelta column 7 days, 23:29:00 day integer column 7

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