Python using while loop with a list name

Question

I am a beginner to python so this might be easy but I am not sure of what the following code means.

q=[start]
    while q:

Does this mean when there is at least one element in the list q execute it and q becomes false when it is empty? Edit:I cannot execute it at the moment and I need to find it quickly.

Answer 1

The line q = [start] means create a variable called q , and assign the value [start] to it . In this case, it will create a list with one element: the value of the variable start . It's the exact same syntax as q = [1, 2] , but it uses a variable instead of a constant value.

After this, the line while q: is a use (or abuse) of Python's type conversion system. While loops require a boolean condition to know whether they should repeat, so your code is equivalent to while bool(q): . To understand how this works, let's examine the possible cases:

bool([1]) == True # This applies for any non-empty list
bool([]) == False # This applies to any empty list

Therefore, the meaning of while q: is actually 'while q is non-empty'.