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sys.argv[1] meaning in script
...more tutorial level.
For every invocation of Python, sys.argv is automatically a list of strings representing the arguments (as separated by spaces) on the command-line. The name comes from the C programming convention in which argv and argc represent the command line arguments.
You'll want to lea...
python generator “send” function purpose?
...t's useful, one of the best use cases I've seen is Twisted's @defer.inlineCallbacks. Essentially it allows you to write a function like this:
@defer.inlineCallbacks
def doStuff():
result = yield takesTwoSeconds()
nextResult = yield takesTenSeconds(result * 10)
defer.returnValue(nextResu...
Difference between __str__ and __repr__?
...e come right out and say it — I do not believe in debuggers. I don’t really know how to use any debugger, and have never used one seriously. Furthermore, I believe that the big fault in debuggers is their basic nature — most failures I debug happened a long long time ago, in a galaxy far far a...
How does the main() method work in C?
...d nothing bad happens with their given compiler.
This is the case if the calling conventions are such that:
The calling function cleans up the arguments.
The leftmost arguments are closer to the top of the stack, or to the base of the stack frame, so that spurious arguments do not invalidate the ...
What does the slash mean in help() output?
...python functions.
Also see the Argument Clinic documentation:
To mark all parameters as positional-only in Argument Clinic, add a / on a line by itself after the last parameter, indented the same as the parameter lines.
and the (very recent addition to) the Python FAQ:
A slash in the argu...
How do I clear only a few specific objects from the workspace?
I would like to remove some data from the workspace. I know the "Clear All" button will remove all data. However, I would like to remove just certain data.
...
Reading a huge .csv file
...
You are reading all rows into a list, then processing that list. Don't do that.
Process your rows as you produce them. If you need to filter the data first, use a generator function:
import csv
def getstuff(filename, criterion):
with ...
How to remove non-alphanumeric characters?
I need to remove all characters from a string which aren't in a-z A-Z 0-9 set or are not spaces.
9 Answers
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Counting array elements in Python [duplicate]
... in an array, because contrary to logic array.count(string) does not count all the elements in the array, it just searches for the number of occurrences of string.
...
Abstract classes in Swift Language
... importantly, notice that there is no dynamic dispatch. When logSalary is called on the instance that is stored as a SoftwareEngineer it calls the overridden version of the method. When logSalary is called on the instance after it has been cast to an Employee, it calls the original implementation (i...