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How do I split a list into equally-sized chunks?
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I’m analyzing some Python code and I don’t know what
pop = population[:]
means. Is it something like array lists in Java or like a bi-dimensional array?
….
Python docs says that slicing a list returns a new list.
Now if a “new” list is being returned I’ve the following questions related to “Assignment to slices”
a = [1, 2, 3]
a[0:2] = [4, 5]
print a
Now the output would be:
[4, 5, 3]
How can something that is returning something come on the left side of expression?
Yes, I read the docs and it say….
In Pandas, when I select a label that only has one entry in the index I get back a Series, but when I select an entry that has more then one entry I get back a data frame.
Why is that? Is there a way to ensure I always get back a data frame?
In [1]: import pandas as pd
In [2]: df = pd.DataFrame(data=range(5), index=[1, 2, 3, 3, 3])
In [3]: type….
So I want to create a list which is a sublist of some existing list.
For example,
L = [1, 2, 3, 4, 5, 6, 7], I want to create a sublist li such that li contains all the elements in L at odd positions.
While I can do it by
L = [1, 2, 3, 4, 5, 6, 7]
li = []
count = 0
for i in L:
if count % 2 == 1:
li.append(i)
count += 1
But I want ….
I am trying to implement slice functionality for a class I am making that creates a vector representation.
I have this code so far, which I believe will properly implement the slice but whenever I do a call like v[4] where v is a vector python returns an error about not having enough parameters. So I am trying to figure out how to define the getit….
This came up in Hidden features of Python, but I can’t see good documentation or examples that explain how the feature works.
….
What are the most common pandas ways to select/filter rows of a dataframe whose index is a MultiIndex?
Slicing based on a single value/label
Slicing based on multiple labels from one or more levels
Filtering on boolean conditions and expressions
Which methods are applicable in what circumstances
Assumptions for simplicity:
input dataframe does ….
Why do the following code samples:
np.array([[1, 2], [2, 3, 4]])
np.array([1.2, “abc”], dtype=float)
…all give the following error?
ValueError: setting an array element with a sequence.
….
I load some machine learning data from a CSV file. The first 2 columns are observations and the remaining columns are features.
Currently, I do the following:
data = pandas.read_csv(‘mydata.csv’)
which gives something like:
data = pandas.DataFrame(np.random.rand(10,5), columns = list(‘abcde’))
I’d like to slice this dataframe in two dataframes: ….