在试图向python字典中添加新键时获得密钥错误Python

Question

在下一段代码中，当我试图向字典中添加一个新键时，我将得到一个KeyError。

def tournamentWinner(competitions, results):
    record = {}
    winner = None
    for i in range(len(results)):
        if results[i] == 0:
            if record[competitions[i][1]] not in record:
                record[competitions[i][1]] = 3
            else:
                record[competitions[i][1]] += 3
        else:
            if record[competitions[i][0]] not in record:
                record[competitions[i][0]] = 3
            else:
                record[competitions[i][0]] += 3
    for element in record:
        if winner is None:
            winner = element
        if element > winner:
            winner = elemnt
    return winner

我得到了这个KeyError：

Exception Detected: 
Traceback (most recent call last):
  File "/tester/program.py", line 7, in tournamentWinner
    if record[competitions[i][1]] not in record:
KeyError: 'C#'

Answer 1

您将得到该错误，因为在使用if- record检查时，record中不存在该键。

您可以通过使用dict.get方法解决这个问题：

而不是这样，如果-否则：

if record[competitions[i][1]] not in record:
                record[competitions[i][1]] = 3
            else:
                record[competitions[i][1]] += 3

您可以使用

record[competitions[i][1]] = record.get(competitions[i][1], 0) + 3