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Why do mutating methods for Python's built-in collection types return nothing instead of the collection itself?


Why do mutating methods for Python's built-in collection types return nothing instead of the collection itself?

By : user2954348
Date : November 22 2020, 01:01 AM
Any of those help To avoid confusion over whether the return value is a copy or not.
To my knowledge, no Python built-in modifies its argument in place and returns the argument itself (stuff like dict.pop and dict.setdefault do return something, but it's not the dict that was mutated), so if you receive a non-None return, you know it's a new object, not the object you called it on. Similarly, if you receive a None return for something that clearly mutates, it must have mutated the argument. This is closely related to the concept of command–query separation; you either do something or return something new, you don't do both at once.
code :


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Can a collection returned by active record be futher filtered using built-in methods?

Can a collection returned by active record be futher filtered using built-in methods?


By : Guilherme Da Silva R
Date : March 29 2020, 07:55 AM
This might help you The first option that springs to mind is Array#select (Ruby 1.9 only):
code :
@collection = UserLevel.all
@filtered_collection = @collection.select { |l| l.blah2_id == 3 }
@filtered_collection = @collection.find_all { |l| l.blah2_id == 3 }
Meteor - return all documents from collection 1 and then query collection 2 as looping through collection 1

Meteor - return all documents from collection 1 and then query collection 2 as looping through collection 1


By : karthik v
Date : March 29 2020, 07:55 AM
I wish did fix the issue. I think there is no need to store it in a hidden element
you can access it by using this._id in authorname helper
code :
<template name="dashboard">
  {{#each eachPost}}
    <p>{{authorName}}</p>
  {{/each}}
</template>

Template.dashboard.helpers({
 eachPost: function()
 {
   return Posts.find({});
 },

 authorName: function()
 {

   console.log(this._id);
   return Authors.findOne({_id: this._id});
 }
});
Does the len() built-in function iterates through the collection to calculate its length, or does it access a collection

Does the len() built-in function iterates through the collection to calculate its length, or does it access a collection


By : user3327495
Date : March 29 2020, 07:55 AM
I think the issue was by ths following , Python built-in collections cache the length in an attribute. Using len() will not iterate over all elements to count them, no.
Keeping the length as an attribute is cheap and easy to maintain. Given that the Python built-in collection types are used so widely, it'd be unwise for them not to do this.
Why do I need Iterators in real life? Without built in C# collection types

Why do I need Iterators in real life? Without built in C# collection types


By : Ravi
Date : March 29 2020, 07:55 AM
Any of those help In your example, the iterator saves you from calculating already calculated fibonacci numbers over and over again. Your second method
code :
public static int Fibonacci(int length)
{
    int a = 0;
    int b = 1;
    for (int i = 0; i < length; i++)
    {
        int temp = a;
        a = b;
        b = temp + b;
    }
    return a;
}
Using constrained generics to return a collection of subtypes as a collection of base types. Compiler not able to infer,

Using constrained generics to return a collection of subtypes as a collection of base types. Compiler not able to infer,


By : xGreen Consulting
Date : March 29 2020, 07:55 AM
hope this fix your issue Covariance only works with reference types.
Your generic constraint must also specify that T is a reference type (class)
code :
static IEnumerable<BaseInterface> GetSubInterfaceImplementers<T>()
        where T : class, BaseInterface
{
        return new GetThings().OfType<T>();
}
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