如何将此代码从 for 循环转换为 while 循环？答案

【问题标题】：How would you convert this code from a for loop to a while loop?如何将此代码从 for 循环转换为 while 循环？
【发布时间】：2023-01-22 11:38:28
【问题描述】：

每次我尝试将其转换为 while 循环时，它都会无休止地循环，任何想法都将不胜感激。如果我使用 for 循环，它运行得非常好，所以我假设使用 while 循环并迭代索引值会获得相同的结果。

from fuzzywuzzy import fuzz
import time
import fitz
from date_check import locate_date

## Each header is a list containing the header text and the form name ##
headers = ["header1", "Header1"]

## cast to lowercase ##
for header in headers:
    header[0] = header[0].lower()

## One of the following is expected to be on the last page of the form ##
end_texts = ["Signature", "Signed"]
## cast to lowercase ##
for i in range(len(end_texts)):
    end_texts[i] = end_texts[i].lower()


## set variables ##
forms = []
first_page = 0
header = ""

## Scan entire document for headers ##
def scan_document(document):
    document = fitz.open(document)
    first_page = False
    last_page = False
    index = 0
    ## This is the loop in question ##
    for i in range(len(document)):
        page = document[i]
        text = page.get_text("text")
        text = text.lower()
        if first_page == False:
            for header in headers:
                if fuzz.partial_ratio(header[0], text) > 90:
                    first_page = i
                    ## Find the date on the page ##
                    date = locate_date(text)
                    forms.append([date, header[1], first_page])
                    break

        elif  first_page != False and last_page == False:
            for end_text in end_texts:
                if end_text in text:
                    last_page = i
                    forms[index].append(last_page)
                    first_page = False
                    last_page = False
                    index += 1
                    break


    ## Return forms list containing first and last page of each form as well as the header ##
    return(forms)

我尝试使用 while 循环并遍历索引，但每当我使用它时程序都会挂起。

## set variables ##
forms = []
first_page = 0
header = ""

## Scan entire document for headers ##
def scan_document(document):
    document = fitz.open(document)
    first_page = False
    last_page = False
    page_num = 0
    index = 0
    
    while page_num <= len(document):
        page = document[page_num]
        text = page.get_text("text")
        text = text.lower()
        if first_page == False:
            for header in headers:
                if fuzz.partial_ratio(header[0], text) > 90:
                    first_page = page_num
                    ## Find the date on the page ##
                    date = locate_date(text)
                    forms.append([date, header[1], first_page])
                    page_num += 1
                    break

        elif  first_page != False and last_page == False:
            for end_text in end_texts:
                if end_text in text:
                    last_page = page_num
                    forms[index].append(last_page)
                    first_page = False
                    last_page = False
                    index += 1
                    page_num += 1
                    break
        else:
            page_num += 1

    ## Return forms list containing first and last page of each form as well as the header ##
    return(forms)```

【问题讨论】：

在某些情况下，你的 page_num += 1 语句都没有被访问。
每次循环迭代只需增加一次page_num。不要把它放在任何条件语句中。以前不是有条件的，为什么它是有条件的是没有意义的。只需在循环的最后一行递增它。
您是否调试过您的程序以检查它是否达到前两个条件的 page_num += 1 行？

标签： python

【解决方案1】：

您需要在每次迭代中增加 page_num，因为某些 if 语句不会被触发。

【讨论】：

【解决方案2】：

page_num += 1行有一些情况，可以在while进入后先增加page_number的值，但是记得用的时候用page_number - 1。

## set variables ##
forms = []
first_page = 0
header = ""


## Scan entire document for headers ##
def scan_document(document):
    document = fitz.open(document)
    first_page = False
    last_page = False
    page_num = 0
    index = 0

    while page_num <= len(document):
        page_num += 1
        page = document[page_num - 1]
        text = page.get_text("text")
        text = text.lower()
        if first_page == False:
            for header in headers:
                if fuzz.partial_ratio(header[0], text) > 90:
                    first_page = page_num - 1
                    ## Find the date on the page ##
                    date = locate_date(text)
                    forms.append([date, header[1], first_page])
                    break

        elif first_page != False and last_page == False:
            for end_text in end_texts:
                if end_text in text:
                    last_page = page_num - 1
                    forms[index].append(last_page)
                    first_page = False
                    last_page = False
                    index += 1
                    break

    ## Return forms list containing first and last page of each form as well as the header ##
    return (forms)

【讨论】：