What you see is the interpreter echoing back the return value of next() in addition to i being printed each iteration: >>> a = iter(list(range(10))) >>> for i in a: … print(i) … next(a) … 0 1 2 3 4 5 6 7 8 9 So 0 is the output of print(i), 1 the return … Read more
The Map interface provides three collection views, which allow a map’s contents to be viewed as a set of keys, collection of values, or set of key-value mappings. The order of a map is defined as the order in which the iterators on the map’s collection views return their elements. Some map implementations, like the … Read more
FIRST UPDATE: Before you try this ever in a production environment (not advised), read this first: http://www.javaspecialists.eu/archive/Issue237.html Starting from Java 9, the solution as described won’t work anymore, because now Java will store strings as byte[] by default. SECOND UPDATE: As of 2016-10-25, on my AMDx64 8core and source 1.8, there is no difference between … Read more
I’d do for i in `seq 0 2 10`; do echo $i; done (though of course seq 0 2 10 will produce the same output on its own). Note that seq allows floating-point numbers (e.g., seq .5 .25 3.5) but bash’s brace expansion only allows integers.
Yes, NSDictionary supports fast enumeration. With Objective-C 2.0, you can do this: // To print out all key-value pairs in the NSDictionary myDict for(id key in myDict) NSLog(@”key=%@ value=%@”, key, [myDict objectForKey:key]); The alternate method (which you have to use if you’re targeting Mac OS X pre-10.5, but you can still use on 10.5 and … Read more
This is the only difference: each: irb> [1,2,3].each { |x| } => [1, 2, 3] irb> x NameError: undefined local variable or method `x’ for main:Object from (irb):2 from :0 for: irb> for x in [1,2,3]; end => [1, 2, 3] irb> x => 3 With the for loop, the iterator variable still lives after … Read more
Can you always turn a recursive function into an iterative one? Yes, absolutely, and the Church-Turing thesis proves it if memory serves. In lay terms, it states that what is computable by recursive functions is computable by an iterative model (such as the Turing machine) and vice versa. The thesis does not tell you precisely … Read more
Built-in support since Handlebars 1.0rc1 Support for this functionality has been added to Handlebars.js, so there is no more need for external helpers. How to use it For arrays: {{#each myArray}} Index: {{@index}} Value = {{this}} {{/each}} For objects: {{#each myObject}} Key: {{@key}} Value = {{this}} {{/each}} Note that only properties passing the hasOwnProperty test … Read more
Assuming you have a class such as >>> class Cls(object): … foo = 1 … bar=”hello” … def func(self): … return ‘call me’ … >>> obj = Cls() calling dir on the object gives you back all the attributes of that object, including python special attributes. Although some object attributes are callable, such as methods. … Read more
df.groupby(‘l_customer_id_i’).agg(lambda x: ‘,’.join(x)) does already return a dataframe, so you cannot loop over the groups anymore. In general: df.groupby(…) returns a GroupBy object (a DataFrameGroupBy or SeriesGroupBy), and with this, you can iterate through the groups (as explained in the docs here). You can do something like: grouped = df.groupby(‘A’) for name, group in grouped: … Read more