在python中读取文本的用途和目的

您所看到的不是有效的python代码,除非 read_text() 是在看不见的地方定义的。函数 读文本() 在标准python中不存在;相反,内置函数 input() 而是为了这个目的。您提供的图像的正确实现是:

def read_float(prompt):                  # prompt is a string, e.g. "Enter a float"
    while True:                          # this is to continue trying if not-a-float is entered
        try:
            number_text = input(prompt)  # this prompts the user for input, and returns a string
            result = float(number_text)  # this tries to convert the string to a float
            break                        # exit this loop to return the float
        except ValueError:               # this is thrown by the previous line if number_text isn't able to be converted to a float
            print('Enter a Number')      # ask the user to try again
    return result

在python控制台中运行此函数的结果:

>>> read_float("Enter a float, please: ")
Enter a float, please: float
Enter a Number
Enter a float, please: 7.5
7.5