大约有 48,000 项符合查询结果（耗时：0.0934秒） [XML]
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.
...
Large, persistent DataFrame in pandas
I am exploring switching to python and pandas as a long-time SAS user.
6 Answers
6
...
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?
...
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?
...
Is there a numpy builtin to reject outliers from a list
...numpy builtin to do something like the following? That is, take a list d and return a list filtered_d with any outlying elements removed based on some assumed distribution of the points in d .
...
Difference between static memory allocation and dynamic memory allocation
...would like to know what is the difference between static memory allocation and dynamic memory allocation?
7 Answers
...
How to write a switch statement in Ruby
...Ruby uses the case expression instead.
case x
when 1..5
"It's between 1 and 5"
when 6
"It's 6"
when "foo", "bar"
"It's either foo or bar"
when String
"You passed a string"
else
"You gave me #{x} -- I have no idea what to do with that."
end
Ruby compares the object in the when clause wit...
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?
...