由previous_page_number（）方法引發的意外異常 - Django Paginator

Question

>>> objects = ['john', 'paul', 'george', 'ringo'] 
>>> p = Paginator(objects, 2) 
>>> p.count 
4 
>>> p.num_pages 
2 
>>> page1 = p.page(1) 
>>> 
>>> page1.previous_page_number() 
Traceback (most recent call last): 
    File "<console>", line 1, in <module> 
    File "C:\Users\Rick\ws2\env\lib\site-packages\django\core\paginator.py", line 136 
, in previous_page_number 
    return self.paginator.validate_number(self.number - 1) 
    File "C:\Users\Rick\ws2\env\lib\site-packages\django\core\paginator.py", line 38, 
in validate_number 
    raise EmptyPage('That page number is less than 1') 
django.core.paginator.EmptyPage: That page number is less than 1 
>>> 

根據previous_page_number()文檔。

Page.previous_page_number()

返回先前的頁碼。如果前一頁不存在，則引發InvalidPage。

我期待previous_page_number()提高InvalidPage例外，如文件所述。爲什麼它返回EmptyPage異常？

我錯過了什麼？

Answer 1

根據分頁程序源（django.core.paginator.py）在1.10：

def validate_number(self, number): 
    """ 
    Validates the given 1-based page number. 
    """ 
    try: 
     number = int(number) 
    except (TypeError, ValueError): 
     raise PageNotAnInteger('That page number is not an integer') 
    if number < 1: 
     raise EmptyPage('That page number is less than 1') 
    if number > self.num_pages: 
     if number == 1 and self.allow_empty_first_page: 
      pass 
     else: 
      raise EmptyPage('That page contains no results') 
    return number 

按照您的條件：數將小於1，因此將提高

EmptyPage('That page number is less than 1')

但根據Django文檔，它應該已經提出了基本異常 InvalidPage！

一邊寫文檔previous_page_number（）

但按照InvalidPage解釋，EmptyPage例外談到下這只是這可能是一個錯字錯。所以它只是一個詳細/派生的InvalidPage異常。