Python 占位符，用于设置每个按键的不同正弦波输出频率

我想使用占位符%f为每个键的正弦波声音输出设置不同的频率。 但是，我收到错误消息“SyntaxError:can't assign to literal”。我检查了我的语法是否不正确，尽管我发现了一个类似的例子——有人能看到问题是什么以及为什么我的代码不能运行吗？ 回溯：文件“test.py”，第50行 （Python，Pygame）

字符串

“%f”

可以是变量名。无法分配

'%f'=261.6

-这是您的错误

“无法分配到文字”

例如，将其命名为

freq

，并用它代替

“%f”

---

顺便说一句：占位符

%f

只能用于字符串格式化（或字符串解析）

---

编辑：

import pygame
from pygame.locals import *

import math
import numpy


def generate_sound(freq):

    #setup our numpy array to handle 16 bit ints, which is what we set our mixer to expect with "bits" up above
    buf = numpy.zeros((n_samples, 2), dtype = numpy.int16)
    max_sample = 2**(bits - 1) - 1

    for s in range(n_samples):
        t = float(s)/sample_rate    # time in seconds
        buf[s][0] = int(round(max_sample*math.sin(2*math.pi*freq*t)))        # left
        buf[s][1] = int(round(max_sample*0.5*math.sin(2*math.pi*freq*t)))    # right

    return pygame.sndarray.make_sound(buf)


bits = 16
#the number of channels specified here is NOT 
#the channels talked about here http://www.pygame.org/docs/ref/mixer.html#pygame.mixer.get_num_channels

pygame.mixer.pre_init(44100, -bits, 2)
pygame.init()

size = (1200, 720)
screen = pygame.display.set_mode(size, pygame.HWSURFACE | pygame.DOUBLEBUF)


duration = 1.0          # in seconds

#this sounds totally different coming out of a laptop versus coming out of headphones

sample_rate = 44100

n_samples = int(round(duration*sample_rate))


#default frequency - not used
sound = None
sound_261_6 = generate_sound(261.6)
sound_293_7 = generate_sound(293.7)

#This will keep the sound playing forever, the quit event handling allows the pygame window to close without crashing
_running = True
while _running:

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            _running = False

        if event.type == KEYDOWN:
            if event.key == K_ESCAPE:
                _running = False
            elif event.key == K_a:
                if not sound:
                    sound = sound_261_6
                    sound.play()

            elif event.key == K_s:
                if not sound:
                    sound = sound_261_6
                    sound.play()

        if event.type == KEYUP:
            if sound:
                sound.stop()
                sound = None

pygame.quit()

---

你应该给我们完整的追踪。只是错误消息没有知道它发生在哪里那么有用。

'%f'=261.6

没有意义-不能将浮点值分配给字符串文字。但是，不清楚您想做什么，所以我无法真正提供答案。文件“test.py”，第50行显示完整的错误消息（回溯）。有多行出现问题-请在代码中标记这一行。数字频率值必须根据每次按键进行更改，才能使用该频率播放声音。谢谢，这是我所需要的，但是，我已将其更改为变量名称，并为其提供了默认频率值440。当按on键时，该频率值应与键相对应，但不会改变。所有按键都有440频的声音。我将更新原始帖子中的代码，以显示它现在所说的内容。如果您更改

freq

，那么您必须再次使用

sin（2*math.pi*freq*t）

调用代码。那么，如何说呢，您必须为范围内的s调用所有代码-

（n\u示例）：

再次调用，非常感谢，不过，我还有一个问题：除了按键和播放音符之间有大约半秒的延迟之外，这个新代码工作得非常出色。这是因为执行for循环所花费的时间，有没有办法消除这种延迟？是的，我举了一个函数的例子，该函数在mainloop（

运行时

）之前生成所有声音。看到我的答案了吗

freq = 261.6

sin(2*math.pi* freq *t)

import pygame
from pygame.locals import *

import math
import numpy


def generate_sound(freq):

    #setup our numpy array to handle 16 bit ints, which is what we set our mixer to expect with "bits" up above
    buf = numpy.zeros((n_samples, 2), dtype = numpy.int16)
    max_sample = 2**(bits - 1) - 1

    for s in range(n_samples):
        t = float(s)/sample_rate    # time in seconds
        buf[s][0] = int(round(max_sample*math.sin(2*math.pi*freq*t)))        # left
        buf[s][1] = int(round(max_sample*0.5*math.sin(2*math.pi*freq*t)))    # right

    return pygame.sndarray.make_sound(buf)


bits = 16
#the number of channels specified here is NOT 
#the channels talked about here http://www.pygame.org/docs/ref/mixer.html#pygame.mixer.get_num_channels

pygame.mixer.pre_init(44100, -bits, 2)
pygame.init()

size = (1200, 720)
screen = pygame.display.set_mode(size, pygame.HWSURFACE | pygame.DOUBLEBUF)


duration = 1.0          # in seconds

#this sounds totally different coming out of a laptop versus coming out of headphones

sample_rate = 44100

n_samples = int(round(duration*sample_rate))


#default frequency - not used
sound = None
sound_261_6 = generate_sound(261.6)
sound_293_7 = generate_sound(293.7)

#This will keep the sound playing forever, the quit event handling allows the pygame window to close without crashing
_running = True
while _running:

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            _running = False

        if event.type == KEYDOWN:
            if event.key == K_ESCAPE:
                _running = False
            elif event.key == K_a:
                if not sound:
                    sound = sound_261_6
                    sound.play()

            elif event.key == K_s:
                if not sound:
                    sound = sound_261_6
                    sound.play()

        if event.type == KEYUP:
            if sound:
                sound.stop()
                sound = None

pygame.quit()