Python IndexError：出了什么问题？

Question

我必须搜索包含日期的字符串，因此我必须找到匹配格式（date_text1、date_text2 和 date_text）的子字符串，并将它们转换为传统格式，例如 25/04/1955。

为什么索引不存在？

import re 

#date_text1 = '042555'
#date_text2 = '04/25/1955'
date_text = 'April 25, 1955'

date_patterns = (r'(\d{2}) (\d{2}) (\d{2})', r'(\d{2}) / (\d{2}) / (\d{4})', r'([\w\D]+) (\d{2}) , (\d{4})')

scan = True
idx = 0
while scan:
    match = re.fullmatch(date_patterns[idx], date_text)
    if match:
        month, day, year = match.groups()
        scan = False
    else:
        idx += 1

# Adjust for years
if int(year) <= 19:
    year = "20"+year
elif int(year) <= 99:
    year = "19"+year

# Adjust for months
months = {"January":"01", "February":"02", "March":"03", "April":"04", "May":"05", "June":"06","July":"07", "August":"08", "September":"09", "October":"10","November":"11", "December":"12"}
if len(month) > 2:
    month = months[month]

normalized_date = f'{day}/{month}/{year}'
print(normalized_date)

Answer 1

因为你的模式都不匹配，循环将不断增加idx直到它超过元组的边界。

不匹配的原因是你的最后一个正则表达式模式有一个小错误。 这个：

r'([\w\D]+) (\d{2}) , (\d{4})')

应该：

r'([\w\D]+) (\d{2}), (\d{4})')

解决这个问题后，我可以从程序中获得正确的输出：

 25/04/1955