Python常用函数

字符串处理

split()

将一个字符串划分成list，划分依据是传入的参数，不传入则默认为空格

txt = "hello my name is Peter"
x = txt.split()
print(x)
>>> ['hello', 'my', 'name', 'is', 'Peter']
x = txt.split("m")
>>> ['hello ', 'y na', 'e is Peter']

strip()
strip() 方法用于移除字符串头尾指定的字符（默认为空格或换行符）或字符序列。

str = "00000003210Runoob01230000000"; 
print str.strip( '0' );  # 去除首尾字符 0

str2 = "   Runoob      ";   # 去除首尾空格
print str2.strip();
>>> 3210Runoob0123
>>> Runoob

数学类

math.atan2(y,x)

按照先y坐标后x坐标输入，输出x轴正向（水平向右）旋转到该点的角度：逆时针为正，顺时针为负，范围为-pi~pi

>>> math.atan2(1,0)*180/3.14159
89.99999998824843
>>> math.atan2(1,-1)*180/3.1415926 
135.00000230285175

tqdm

model.train()
for epoch in range(1, 5):
    with tqdm(train_loader, unit="batch") as tepoch:			#新增
        for data, target in tepoch:
            tepoch.set_description(f"Epoch {epoch}")			# 新增
            
            data, target = data.to(device), target.to(device)
            optimizer.zero_grad()
            output = model(data)
            predictions = output.argmax(dim=1, keepdim=True).squeeze()
            loss = F.nll_loss(output, target)
            correct = (predictions == target).sum().item()
            accuracy = correct / batch_size
            
            loss.backward()
            optimizer.step()

            tepoch.set_postfix(loss=loss.item(), accuracy=100. * accuracy)	#新增
            sleep(0.1)

显示结果为：

Epoch 1: 15%|▉ | 142/937 [00:16<01:32, 8.56batch/s, accuracy=89.1, loss=0.341]