For and While
If we want to do some operation or set of operations various times, we can handle the process in several different types. The most straightforward types are for and while statements (often called for and while loops).
A for loop has the following form:
for in :
...
The interpreter starts by calculating listExpr. If it does not yield a list, tuple, or string7, an error occurs. If it does yield a list-like structure or list, then the block of instructions will, under normal conditions, be executed one time for every value in that list. At the end, the variable will remain bound to the last element of the list (and if it had a useful value before the for was calculated, that number will have been permanently overwritten).
Here is a basic for loop:
result = 0
for x in [1, 3, 4]:
result = result + x * x
At the end of this execution, result will give the value 26, and x will have the value 4.
One situation in which the body is not executed once for each value in the list is when a return statement is encountered. No situations whether value is nested in a structure or not, if it is calculated it immediately gives a problem a value to be returned from a function call. So, for example, we may write a function that tests to see if an item is a member of a list, and gives True if it is and 0 if it is not, as given:
def member(x, items):
for i in items:
if x == i:
return True return False
The procedure loops through all of the components in items, and relates them to x. As soon as it ?nds an item i that is same to x, it can quit and return the value True from the method. If it has all the way through the loop without giving any value, then we know that x is not in the structure, and we may give False