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NSUserDefaults - How to tell if a key exists
I'm working on a small iPhone app, and I am using NSUserDefaults as my data persistence. It only has to keep track of a few things, such as some names and some numbers so I figure I might as well keep it simple.
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Large, persistent DataFrame in pandas
I am exploring switching to python and pandas as a long-time SAS user.
6 Answers
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What does the Ellipsis object do?
...nterpretation is purely up to whatever implements the __getitem__ function and sees Ellipsis objects there, but its main (and intended) use is in the numpy third-party library, which adds a multidimensional array type. Since there are more than one dimensions, slicing becomes more complex than just...
How to convert a string to lower case in Bash?
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The are various ways:
POSIX standard
tr
$ echo "$a" | tr '[:upper:]' '[:lower:]'
hi all
AWK
$ echo "$a" | awk '{print tolower($0)}'
hi all
Non-POSIX
You may run into portability issues with the following examples:
Bash 4.0
$ echo "${a,,}"
hi all...
What's the difference between ISO 8601 and RFC 3339 Date Formats?
ISO 8601 and RFC 3339 seem to be two formats that are common the web. Should I use one over the other? Is one just an extension? Do I really need to care that bad?
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Finding sum of elements in Swift array
...the sum of an array of integers in swift?
I have an array called multiples and I would like to know the sum of the multiples.
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Missing return statement in a non-void method compiles
...ered a situation where a non-void method is missing a return statement and the code still compiles.
I know that the statements after the while loop are unreachable (dead code) and would never be executed. But why doesn't the compiler even warn about returning something? Or why would a language...
Python constructors and __init__
Why are constructors indeed called "Constructors"? What is their purpose and how are they different from methods in a class?
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Express.js - app.listen vs server.listen
... get it. What is the difference between creating an app using Express.js and starting the app listening on port 1234, for example:
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In Python, how do I iterate over a dictionary in sorted key order?
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This is not obvious. In fact, items() creates a list and therefore uses memory, whereas iteritems() essentially does not use memory. What to use mostly depend on the size of the dictionary. Furthermore, the automatic Python 2 to Python 3 conversion tool (2to3) automatically tak...