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Default value to a parameter while passing by reference in C++
...efault any argument you wish:
class A {};
class B {};
class C {};
void foo (A const &, B const &, C const &);
void foo (B const &, C const &); // A defaulted
void foo (A const &, C const &); // B defaulted
void foo (C const &); // A & B defaulted etc...
It i...
How to unit test an object with database queries
...jection pattern, as in the following pseudo-code:
class Bar
{
private FooDataProvider _dataProvider;
public instantiate(FooDataProvider dataProvider) {
_dataProvider = dataProvider;
}
public getAllFoos() {
// instead of calling Foo.GetAll() here, we are introducing...
What is the difference between join and merge in Pandas?
...ys use join on indices:
import pandas as pd
left = pd.DataFrame({'key': ['foo', 'bar'], 'val': [1, 2]}).set_index('key')
right = pd.DataFrame({'key': ['foo', 'bar'], 'val': [4, 5]}).set_index('key')
left.join(right, lsuffix='_l', rsuffix='_r')
val_l val_r
key
foo 1 4
ba...
Concatenate two slices in Go
...}, []int{3,4}...)
This is just like any other variadic function.
func foo(is ...int) {
for i := 0; i < len(is); i++ {
fmt.Println(is[i])
}
}
func main() {
foo([]int{9,8,7,6,5}...)
}
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...
TypeError: 'NoneType' object is not iterable in Python
...erable
Python methods return NoneType if they don't return a value:
def foo():
print("k")
a, b = foo() #TypeError: 'NoneType' object is not iterable
You need to check your looping constructs for NoneType like this:
a = None
print(a is None) #prints True
print(a is not No...
Singleton pattern in nodejs - is it needed?
... are loaded. This means
(among other things) that every call to require('foo') will get
exactly the same object returned, if it would resolve to the same
file.
Multiple calls to require('foo') may not cause the module code to be
executed multiple times. This is an important feature. Wit...
What are the differences between Abstract Factory and Factory design patterns?
......
What they're saying is that there is an object A, who wants to make a Foo object. Instead of making the Foo object itself (e.g., with a factory method), it's going to get a different object (the abstract factory) to create the Foo object.
Code Examples
To show you the difference, here is a fact...
How do I check if a string is valid JSON in Python?
...print is_json('{"age":100 }') #prints True
print is_json('{"foo":[5,6.8],"foo":"bar"}') #prints True
Convert a JSON string to a Python dictionary:
import json
mydict = json.loads('{"foo":"bar"}')
print(mydict['foo']) #prints bar
mylist = json.loads("[5,6,7]")
print(mylist)
[5, ...
What is a “callable”?
...
Called when the instance is ''called'' as a function
Example
class Foo:
def __call__(self):
print 'called'
foo_instance = Foo()
foo_instance() #this is calling the __call__ method
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...
What's the difference between passing by reference vs. passing by value?
...here's an example in some C-like language of a function declaration:
void foo(int param) { // line 1
param += 1;
}
And here's an example of calling this function:
void bar() {
int arg = 1; // line 2
foo(arg); // line 3
}
Using this example, I want to define some important bits of t...