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每次我运行我的代码时，它都会告诉我总数没有定义。我在 support.py 中定义了它，然后将其导入到 stop.py 中。我一直在寻找类似的案例，但我不明白为什么它告诉我这个。请帮忙！

这是停止.py

from support import *

def main():

    def get_info():
      amplitude = float(input("Amplitude of the sine wave (in feet): "))
      period = float(input("Period of the sine wave (in feet): "))
      sign = float(input("Distance to the stop sign (in feet): "))
      nobrake = float(input("Distance needed to stop without using hand brakes (in feet): "))
      step = 9
      return amplitude, period, sign, nobrake

    get_info()

    get_distance(0, 0, 155.3, 134.71)

    print("Distance to the stop sign (in feet): 155.3")
    print("Distance needed to stop without using hand brakes (in feet): 350.5")
    print("Length of the sine wave: ", total)

main()

这是 support.py

import math

def get_sine_length(amplitude, period, x_distance, step):
  x = 0.0
  total = 0.0
  last_x = 0
  last_y = 0
  while x <= x_distance + (step / 2):
     y = math.sin(2 * math.pi / period * x) * amplitude
     dist = get_distance(last_x, last_y, x, y)
     #print("distance from (", last_x, ",", last_y, ") to (", x, ",", y, ") is", dist)
     total = total + dist
     last_x = x
     last_y = y
     x = x + step
 return total

def get_distance(a, b, c, d):
   dx = c - a
   dy = d - b
   dsquared = dx**2 + dy**2
   result = math.sqrt(dsquared)
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1 回答 1

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total是本地的get_sine_length。由于您要返回它，因此要调用它get_sine_length并存储结果。

这个问题实际上与真的没有任何关系import。如果 for 的函数定义get_sine_length在stopping.py. 在函数内部（在 a 内部def someFunc():）定义的变量只能由该函数访问，除非您强制它们是全局的。然而，大多数时候，你不应该仅仅为了从函数外部访问通常的局部变量而声明全局变量——这就是返回的目的。

此示例显示了您遇到的一般问题。我不愿称其为问题，因为它实际上是 python（以及许多其他编程语言）的一个重要语言特性。

>>> def func():
...     localVar = "I disappear as soon as func() is finished running."
... 
>>> print localVar
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'localVar' is not defined
>>> func()
>>> print localVar
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'localVar' is not defined

将函数想象成一台接受某些输入并输出其他输入的机器。您通常不想打开机器 - 您只想输入输入并获得输出。

于 2012-10-20T00:07:30.167 回答