Python 2.7 尝试并排除 ValueError

Question

我使用 int(raw_input(...)) 查询预期为 int 的用户输入

然而，当用户没有输入整数时，即只是点击回车，我得到一个 ValueError。

def inputValue(inputMatrix, rangeRows, rangeCols, defaultValue, playerValue):
    rowPos = int(raw_input("Please enter the row, 0 indexed."))
    colPos = int(raw_input("Please enter the column, 0 indexed."))
    while True:
        #Test if valid row col position and position does not have default value
        if rangeRows.count(rowPos) == 1 and rangeCols.count(colPos) == 1 and inputMatrix[rowPos][colPos] == defaultValue:
            inputMatrix[rowPos][colPos] = playerValue
            break
        else:
            print "Either the RowCol Position doesn't exist or it is already filled in."
            rowPos = int(raw_input("Please enter the row, 0 indexed."))
            colPos = int(raw_input("Please enter the column, 0 indexed."))
    return inputMatrix

我试着变聪明，使用 try 和 except 来捕获 ValueError，向用户打印警告，然后再次调用 inputValue()。然后当用户输入 return 到查询时它会工作但是当用户正确输入整数时它会倒下

下面是修改后的带有try and except的部分代码:

def inputValue(inputMatrix, rangeRows, rangeCols, defaultValue, playerValue):
    try:
        rowPos = int(raw_input("Please enter the row, 0 indexed."))
    except ValueError:
        print "Please enter a valid input."
        inputValue(inputMatrix, rangeRows, rangeCols, defaultValue, playerValue)   
    try:
        colPos = int(raw_input("Please enter the column, 0 indexed."))
    except ValueError:
        print "Please enter a valid input."
        inputValue(inputMatrix, rangeRows, rangeCols, defaultValue, playerValue)   

Answer 1

一个快速而肮脏的解决方案是:

parsed = False
while not parsed:
    try:
        x = int(raw_input('Enter the value:'))
        parsed = True # we only get here if the previous line didn't throw an exception
    except ValueError:
        print 'Invalid value!'

这将一直提示用户输入，直到 parsed 为 True，这只会在没有异常的情况下发生。