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pandas GroupBy columns with NaN (missing) values
...cient topic, if someone still stumbles over this--another workaround is to convert via .astype(str) to string before grouping. That will conserve the NaN's.
df = pd.DataFrame({'a': ['1', '2', '3'], 'b': ['4', np.NaN, '6']})
df['b'] = df['b'].astype(str)
df.groupby(['b']).sum()
a
b
4 1
6 ...
How to check for a valid URL in Java?
...hat you can set to control how this class behaves, by default http, https, and ftp are accepted.
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What's the difference between an argument and a parameter?
...ng else. Either way the other people know what I mean, but what's correct, and what's the history of the terms?
34 Answers
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How to elegantly check if a number is within a range?
How can I do this elegantly with C# and .NET 3.5/4?
27 Answers
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Confused about __str__ on list in Python [duplicate]
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Python has two different ways to convert an object to a string: str() and repr(). Printing an object uses str(); printing a list containing an object uses str() for the list itself, but the implementation of list.__str__() calls repr() for the individual it...
Using arrays or std::vectors in C++, what's the performance gap?
...hould be avoided. There is the problem you have to keep track of the size, and you need to delete them manually and do all sort of housekeeping.
Using arrays on the stack is also discouraged because you don't have range checking, and passing the array around will lose any information about its siz...
Setting the correct encoding when piping stdout in Python
..."åäö".encode('utf-8')
Another didactic example is a Python program to convert between ISO-8859-1 and UTF-8, making everything uppercase in between.
import sys
for line in sys.stdin:
# Decode what you receive:
line = line.decode('iso8859-1')
# Work with Unicode internally:
line...
Android 4.1: How to check notifications are disabled for the application?
Android 4.1 offers the user a check box to disable notifications for a specific application.
6 Answers
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What is the maximum possible length of a .NET string?
...owhere near that. Since no single object in a .NET program may be over 2GB and the string type uses UTF-16 (2 bytes for each character), the best you could do is 1,073,741,823, but you're not likely to ever be able to allocate that on a 32-bit machine.
This is one of those situations where "If you ...
How does delete[] know it's an array?
...eed the delete[] syntax at all? Why can't a single delete form be used to handle all deletes?
The answer to this goes back to C++'s roots as a C-compatible language (which it no longer really strives to be.) Stroustrup's philosophy was that the programmer should not have to pay for any features tha...