请写出完整的python代码，实现利用ylov5对包含任意数量香蕉的照片进行计数，并且利用pyqt设计一个界面，实现从文件夹选择图像，显示所选择的图像，点击按钮开始计数，输出计数结果和结果图像四个功能

以下是实现您描述的功能的Python代码，使用了yolov5和PyQt库：

import sys
import os
from PyQt5.QtWidgets import QApplication, QWidget, QVBoxLayout, QLabel, QPushButton, QFileDialog
from PyQt5.QtGui import QPixmap
import torch
import cv2
from PIL import Image
from yolov5 import detect

class BananaCounter(QWidget):
    def __init__(self):
        super().__init__()
        self.init_ui()

    def init_ui(self):
        self.setWindowTitle("Banana Counter")
        self.setGeometry(100, 100, 400, 300)

        self.image_label = QLabel(self)
        self.result_label = QLabel(self)
        self.result_label.setGeometry(10, 200, 380, 50)
        self.result_label.setStyleSheet("font-size: 16px; color: red")

        self.select_button = QPushButton("Select Image", self)
        self.select_button.setGeometry(10, 10, 120, 30)
        self.select_button.clicked.connect(self.select_image)

        self.count_button = QPushButton("Start Counting", self)
        self.count_button.setGeometry(150, 10, 120, 30)
        self.count_button.clicked.connect(self.count_bananas)

        self.layout = QVBoxLayout()
        self.layout.addWidget(self.image_label)
        self.layout.addWidget(self.result_label)
        self.layout.addWidget(self.select_button)
        self.layout.addWidget(self.count_button)

        self.setLayout(self.layout)

    def select_image(self):
        file_dialog = QFileDialog()
        image_path, _ = file_dialog.getOpenFileName(self, "Select Image", filter="Image Files (*.png *.jpg)")
        if image_path:
            self.show_selected_image(image_path)

    def show_selected_image(self, image_path):
        pixmap = QPixmap(image_path)
        self.image_label.setPixmap(pixmap.scaled(380, 180))

    def count_bananas(self):
        image_path = self.get_selected_image_path()
        if image_path:
            result_image_path, count = self.detect_bananas(image_path)
            self.show_result(count)
            self.show_result_image(result_image_path)

    def get_selected_image_path(self):
        if self.image_label.pixmap():
            return self.image_label.pixmap().toImage().text()
        return None

    def detect_bananas(self, image_path):
        weights = 'path/to/your/yolov5/weights.pt'
        device = torch.device('cuda' if torch.cuda.is_available() else 'cpu')

        # Load model
        model = torch.hub.load('ultralytics/yolov5', 'custom', path=weights)
        model.to(device).eval()

        # Load image
        img = Image.open(image_path)

        # Inference
        results = model(img)

        # Get result image path
        result_image_path = os.path.splitext(image_path)[0] + '_result.jpg'
        results.save(result_image_path)

        # Count bananas
        count = len(results.pred)

        return result_image_path, count

    def show_result(self, count):
        self.result_label.setText(f"Banana Count: {count}")

    def show_result_image(self, result_image_path):
        pixmap = QPixmap(result_image_path)
        self.result_label.setPixmap(pixmap.scaled(380, 50))


if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = BananaCounter()
    window.show()
    sys.exit(app.exec_())

请将 `path/to/your/yolov5/weights.pt` 替换为实际的yolov5权重文件路径。另外，您需要在您的环境中安装PyQt和yolov5库，可以使用以下命令进行安装：

pip install PyQt5 torch torchvision opencv-python Pillow
pip install git+https://github.com/ultralytics/yolov5.git

请确保您的环境已安装正确的依赖项。运行代码后，将会弹出一个界面，您可以选择图像文件，点击“Start Counting”按钮进行香蕉计数，并在界面上显示计数结果和结果图像。