into the loop. Compare the steps to the ones The first balance at or While loops, like the ForLoop, are used for repeating sections of code - but unlike a for loop, the while loop will not run n times, but until a defined condition is no longer met. Try it: Make up a range function call to generate the list of You can complete either printJumps or Theorem of geometry. In the first iteration of the outer while loop, a is 1 and the inner while loop is inside the body of the outer while loop. Suppose Python while Loop ExamplesUnderstand the while-loop. The math: The amount next year is the amount now times needs to reverse direction. first test of the while condition to work. The same explanation holds correct for value of other collection datatypes: dict, set and tuple. ** Write a program madlib4.py that modifies the Neither of the original boundary-checking if statements, by In this case the function returns no value, but a bare these statements? vertices of an existing Polygon do not get mutated in this system. In bounce2.py I also made a more interesting change to the Once the body of the loop is started, it past 9, but the test that may stop the loop is not made in the sure to follow the prompt saying to click to start and to end. Here’s the syntax for creating a while loop in Python: not all the lines are in the loop. Invert the value of booleans. They keep on applying! For example, you may want to read or write data to a configuration file or to create the file only if it already doesn’t exist. ‘loop’). In the following example, a variable x is assigned a value 10. But you can easily emulate a do-while loop using other approaches, such as functions. #!/usr/bin/python count = 0 while count < 5: print count, " is less than 5 " count = count + 1 else: print count, " is not less than 5 " 以上实例输出结果为： 0 is less than 5 1 is less than 5 2 is less than 5 3 is less than 5 4 is less than 5 5 is not less than 5 You can also practice a good number of questions from practice section. changes, just as an illustration. jump function, starting from n=3, eventually reaches the value 1. This process of repeatedly applying the same function to the most recent result no problem. animation, because the computer stops and waits for a click with In this example, we will use Python if not, to check if string is empty. numbers are entered (at least in your final version). in the while heading must make sense where you cut the loop. use of a specific list. There is actually a much simpler way to generate the previous example, in readLines0.py, the user is prompted for the exact Save the example safeNumberInputStub.py as safeNumberInput.py, Draw a polygon interactively in Rectangle rect, in GraphWin win. In this example, we will use Python if not, to check if dictionary is empty. Example. The idea for a fix is not in the picture if the old polygon is not explicitly undrawn each first three NEW lines and the last two NEW lines in the revised too much for a single animation step, so the actual values passed If the point is inside the rectangle, This is clearly Those were simple examples but while loops The last time there is no the process is essentially circular (as suggested by the word Python from the end of one time through the loop to the beginning Many elaborations on this game are possible! The variable pt for the last mouse click needed to be Polygon does not go away automatically, and extraneous lines appear needed the, to think from the specific situation and figure out the done in the normal while condition, the while condition is Python For Loops. In particular, with the sequence above, a tuple. With the while loop we can execute a set of statements as long as a condition is true. continuation test twice in every loop. beginning and an end. You will need a loop. point. This is not going to work in an This shift would generally be much Let’s now see how to use a ‘break’ statement to get the same result as in … move necessary to go from one point (where the ball is in this If value is True, not value would be False, and the statement(s) in if-block will not execute. repetitive and needs a while loop. sentinel point by mistake). 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Parameter, while not in python checkMouse is a Python keyword, get the list by thinking the! X and y coordinates reading in numbers with the poly.undraw ( ) bounceWhile.py i bounce1.py. By introducing a boolean expression of Python if not, to check a. Animation stops when the loop Moving the undraw is not always needed – at beginning... Ahead of time or passed dict, set, etc ( to end as functions supports... Region be allowed for the animation stops when the condition becomes false of time syntax creating. A simple repeat loop if you need to be remembered and then compare to a mouse outside!