truthiness

import numpy as np a = np.array([0]) b = np.array([None]) c = np.array(['']) d = np.array([' ']) Why should we have this inconsistency: >>> bool(a) False >>> bool(b) False >>> bool(c) True >>> bool(d) False Alex Riley For arrays with one element, the array's truth value is determined by the truth value of that element. The main point to make is that np.array(['']) is not an array containing one empty Python string. This array is created to hold strings of exactly one byte each and NumPy pads strings that are too short with the null character. This means that the array is equal to np.array(['\0

Let's say I have a something like true && true #=> true Which makes sense, so I try something like: true && "dsfdsf" #=> "dsfdsf" Which surprises me because often times I'll do something like if something && something and I always thought that that was evaluating to true and would return true. Further experimentation doing things like: jruby-1.7.3 :009 > "ad" && "dsf" => "dsf" jruby-1.7.3 :010 > "ad" && "sdfd" && nil => nil jruby-1.7.3 :011 > "ad" && nil && "sdf" => nil makes it seem like Ruby returns either the last value if all are true or the first false value it finds. Why does it do this?

I am learning python, but I'm a bit confused by the following result. In [41]: 1 == True Out[41]: True In [42]: if(1): ...: print('111') ...: 111 In [43]: ... == True Out[43]: False <===== why this is False while '1 == True' is True in previous sample In [44]: if (...): <==== here ... just behaves like True ...: print('...') ...: ... According to the documentation , ... has a truth value of True. But I still feel the above code a bit inconsistent. ...And something more interesting: In [48]: 2==True Out[48]: False <===== why 1==True returns True while 2==True returns False? In [49]: if(2): ...:

Is something wrong with js? if("hello".indexOf("world")) { // I forgot to add > -1 here console.log("hello world"); } Basically if(-1) is true. How is this possible? It took me a whole day to fix this. Is there a list available where these kind of things are listed? Or tools available to catch things like these. As per ECMA 5.1 Standard Specifications , the following table is used to determine the truthyness of an expression +-----------------------------------------------------------------------+ | Argument Type | Result | |:--------------|-----------------------------------------------------

Was just doing some testing and I find this odd: [] == false Gives true, this makes sense because double equal only compares contents and not type and tries to do type-coercion. But if its comparing contents and returns true, that means [ ] is falsey (if you did [] == true you get false too), which means: [] || false Should give false, but it gives [ ], making it truthy? Why? Another example: "\n " == 0 Gives true, but "\n " || false gives "\n " ? Is there an explanation for this or its just an oddity. When I tried this in C, we get: int x = "\n " == 0; printf("%d\n", x); int y = "\n " || 0;