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Anton Buketov
Asked:2022-01-04 17:42:55 +0000 UTC2022-01-04 17:42:55 +0000 UTC

变量计数错误

  • 772
print("start")
start = {"x":20, "y":20};
print(start)
print("startingPos")
startingPos = start;
print(startingPos)

def refreshCoords(directions,startingPos):
    if directions == "^":
        startingPos = {"x":startingPos["x"], "y":startingPos["y"]+1};
    if directions == "v":
        startingPos = {"x":startingPos["x"], "y":startingPos["y"]-1};
        return startingPos  
    if directions == ">":
        startingPos = {"x":startingPos["x"]+1, "y":startingPos["y"]};
    if directions == "<":
        startingPos = {"x":startingPos["x"]-1, "y":startingPos["y"]}; 

def walker(direction,startingPos):
    print(refreshCoords(direction,startingPos))

for i in range(1,10,1):
    walker("v",startingPos)

我需要帮助解释，我不明白为什么在调用 walker("v",startingPos) 时，"Y" 只更改一次，然后值重复。它必须根据需要更改多次（在此示例中，调用函数时它从 20 更改为 10）。这段代码有什么错误？

python

1 个回答

  1. Best Answer

    关键是你在函数中改变局部变量 startingPos的值而不以任何方式影响全局变量 startingPos

    这可以绕过，例如，return

    print("start")
start = {"x":20, "y":20}
print(start)
print("startingPos")
startingPos = start
print(startingPos)

def refreshCoords(directions, oldPos):
    newPos = oldPos

    if directions == "^":
        newPos = {"x":oldPos["x"], "y":oldPos["y"]+1}
    if directions == "v":
        newPos = {"x":oldPos["x"], "y":oldPos["y"]-1}
    if directions == ">":
        newPos = {"x":oldPos["x"]+1, "y":oldPos["y"]}
    if directions == "<":
        newPos = {"x":oldPos["x"]-1, "y":oldPos["y"]}

    return newPos


def walker(direction, oldPos):
    newPos = refreshCoords(direction, oldPos)
    print(newPos)
    return newPos


newPos = startingPos
for i in range(1,10,1):
    newPos = walker("v",newPos)
    • 3

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