if __name__ == '__main__': if sys.argv[1:]: target_path = sys.argv[1] main(target_path)这段代码是什么意思
时间: 2023-07-21 18:52:16 浏览: 52
这段代码是 Python 中常用的判断模块,用于判断是直接运行当前脚本还是作为模块导入其他脚本中。如果当前脚本是主程序执行的,则代码会执行 if __name__ == '__main__': 中的代码块。
代码块中第二行 if sys.argv[1:]: 是判断命令行参数是否存在,如果存在则将第一个参数赋值给变量 target_path。
最后一行 main(target_path) 是调用 main 函数,将 target_path 作为参数传入。其中 main 函数是由程序员自行编写的函数,根据具体情况而定。
相关问题
编写程序,使用多线程技术把源文件夹及其子文件夹中所有内容都复制指定的目标文件夹中。要求该程序能够通过命令行参数来指定源文件夹和目标文件夹以及线程数量。
以下是一个使用Python语言实现的多线程复制文件的程序:
```python
import os
import shutil
import sys
import threading
def copy(src, dst):
try:
if os.path.isdir(src):
shutil.copytree(src, dst)
else:
shutil.copy2(src, dst)
except Exception as e:
print(e)
def copy_files(src, dst, num_threads):
threads = []
for root, dirs, files in os.walk(src):
for filename in files:
src_path = os.path.join(root, filename)
dst_path = os.path.join(dst, os.path.relpath(src_path, src))
if not os.path.exists(os.path.dirname(dst_path)):
os.makedirs(os.path.dirname(dst_path))
while len(threads) >= num_threads:
for t in threads:
if not t.is_alive():
threads.remove(t)
break
t = threading.Thread(target=copy, args=(src_path, dst_path))
t.start()
threads.append(t)
for t in threads:
t.join()
if __name__ == '__main__':
if len(sys.argv) < 4:
print("Usage: python copy_files.py <src_folder> <dst_folder> <num_threads>")
else:
src_folder = sys.argv[1]
dst_folder = sys.argv[2]
num_threads = int(sys.argv[3])
copy_files(src_folder, dst_folder, num_threads)
```
该程序使用了Python标准库中的os和shutil模块来操作文件和文件夹,使用threading模块创建多线程来并行复制文件。在copy_files函数中,首先通过os.walk遍历源文件夹中的所有文件和文件夹,然后对每个文件创建一个新的线程来执行复制操作。如果当前线程数量已经达到指定的最大线程数量,程序将等待某个线程完成后再创建新的线程,以避免同时创建过多线程导致系统资源不足。最后,程序等待所有线程执行完毕后退出。
用Python-pyqt5制作一个可以打开音频文件,一边播放音频一边同时显示波形和FFT波形两个窗口的,带按键的多线程程序
以下是一个Python-pyqt5制作的可以打开音频文件,一边播放音频一边同时显示波形和FFT波形两个窗口的,带按键的多线程程序的示例代码:
```python
import sys
import os
import threading
import time
import numpy as np
import wave
from scipy import fftpack
from PyQt5.QtWidgets import QApplication, QWidget, QPushButton, QFileDialog, QVBoxLayout
from PyQt5.QtGui import QPainter, QPen
from PyQt5.QtCore import Qt, QThread, pyqtSignal, QPointF
class AudioPlayer(QWidget):
def __init__(self):
super().__init__()
self.setWindowTitle("Audio Player")
self.setGeometry(100, 100, 800, 600)
self.audio_file_path = None
self.audio_data = None
self.audio_data_size = None
self.audio_frames_per_second = None
self.audio_num_channels = None
self.audio_sample_width = None
self.audio_duration = None
self.play_button = QPushButton("Play")
self.play_button.clicked.connect(self.play_audio)
self.open_button = QPushButton("Open")
self.open_button.clicked.connect(self.open_audio_file)
self.fft_button = QPushButton("FFT")
self.fft_button.clicked.connect(self.show_fft)
self.waveform = Waveform()
self.fft_waveform = Waveform()
self.layout = QVBoxLayout()
self.layout.addWidget(self.play_button)
self.layout.addWidget(self.open_button)
self.layout.addWidget(self.fft_button)
self.layout.addWidget(self.waveform)
self.layout.addWidget(self.fft_waveform)
self.setLayout(self.layout)
self.player_thread = None
self.player_thread_exit_flag = False
self.fft_thread = None
self.fft_thread_exit_flag = False
def open_audio_file(self):
self.audio_file_path, _ = QFileDialog.getOpenFileName(self, "Open Audio File", os.getenv("HOME"), "Audio Files (*.wav)")
if self.audio_file_path:
self.read_audio_file()
self.waveform.set_data(self.audio_data, self.audio_frames_per_second, self.audio_num_channels)
self.fft_waveform.set_data(self.audio_data, self.audio_frames_per_second, self.audio_num_channels)
def read_audio_file(self):
with wave.open(self.audio_file_path, "rb") as wf:
self.audio_data_size = wf.getnframes()
self.audio_frames_per_second = wf.getframerate()
self.audio_num_channels = wf.getnchannels()
self.audio_sample_width = wf.getsampwidth()
self.audio_duration = self.audio_data_size / self.audio_frames_per_second
self.audio_data = np.frombuffer(wf.readframes(self.audio_data_size), dtype=np.int16)
def play_audio(self):
if not self.audio_file_path:
return
if self.player_thread and self.player_thread.is_alive():
self.player_thread_exit_flag = True
self.player_thread.join()
self.player_thread_exit_flag = False
self.play_button.setText("Play")
return
self.player_thread = threading.Thread(target=self.play_audio_thread)
self.player_thread.start()
self.play_button.setText("Stop")
def play_audio_thread(self):
audio = self.audio_data.copy()
p = pyaudio.PyAudio()
stream = p.open(format=p.get_format_from_width(self.audio_sample_width),
channels=self.audio_num_channels,
rate=self.audio_frames_per_second,
output=True)
chunk_size = 1024
chunk_index = 0
while chunk_index * chunk_size < len(audio) and not self.player_thread_exit_flag:
start_index = chunk_index * chunk_size
end_index = start_index + chunk_size
chunk = audio[start_index:end_index].tobytes()
stream.write(chunk)
chunk_index += 1
stream.stop_stream()
stream.close()
p.terminate()
self.play_button.setText("Play")
def show_fft(self):
if not self.audio_file_path:
return
if self.fft_thread and self.fft_thread.is_alive():
self.fft_thread_exit_flag = True
self.fft_thread.join()
self.fft_thread_exit_flag = False
self.fft_button.setText("FFT")
return
self.fft_thread = threading.Thread(target=self.show_fft_thread)
self.fft_thread.start()
self.fft_button.setText("Stop")
def show_fft_thread(self):
audio = self.audio_data.copy()
fft_size = 1024
fft_sample_rate = self.audio_frames_per_second // fft_size
fft_num_samples = len(audio) // fft_size * fft_size
audio = audio[:fft_num_samples].reshape(-1, fft_size)
fft_data = fftpack.fft(audio, axis=1)
fft_data = np.abs(fft_data[:, :fft_size//2])
self.fft_waveform.set_data(fft_data, fft_sample_rate, 1)
while not self.fft_thread_exit_flag:
time.sleep(0.1)
self.fft_button.setText("FFT")
class Waveform(QWidget):
def __init__(self):
super().__init__()
self.data = None
self.sample_rate = None
self.num_channels = None
def set_data(self, data, sample_rate, num_channels):
self.data = data
self.sample_rate = sample_rate
self.num_channels = num_channels
self.update()
def paintEvent(self, event):
if not self.data:
return
painter = QPainter(self)
painter.setRenderHint(QPainter.Antialiasing)
pen = QPen(Qt.green)
pen.setWidth(2)
painter.setPen(pen)
width = self.width()
height = self.height()
data_size = len(self.data)
step_size = data_size // width
scale_factor = height / (2 ** 16)
for channel in range(self.num_channels):
points = []
for i in range(width):
start_index = i * step_size
end_index = start_index + step_size
data_slice = self.data[start_index:end_index, channel]
mean_value = np.mean(data_slice)
y = height / 2 - mean_value * scale_factor
points.append(QPointF(i, y))
painter.drawPolyline(points)
if __name__ == "__main__":
app = QApplication(sys.argv)
audio_player = AudioPlayer()
audio_player.show()
sys.exit(app.exec_())
```
需要注意的几点:
1. 这个程序使用了多线程,一个用于播放音频,一个用于显示FFT波形。
2. 程序中使用了PyAudio和wave库来读取和播放音频。
3. Waveform类用于显示音频波形,FFT波形类似,只是把数据转换为FFT之后再绘制。
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