UnboundLocalError：分配前已引用局部变量“ strdate”

Question

When I tried this codes with 3-4 files as a test, it worked fine. But when I ran with 3,000+ files, the error message popped up saying File "C:\\Users\\dul\\Dropbox\\Article\\ap_final.py", line 51, in extract_data combid = matchcomp2 + "," + strdate + "," + matchw + "," + matchcount UnboundLocalError: local variable 'strdate' referenced before assignment

I searched and it looks like something with global is an issue. I simply do not understand what that means..Please help.

import os,csv,datefinder,re
import numpy as np

os.chdir('C:\Users\dul\Dropbox\Article\parsedarticles')

def matchwho(text_to_match):
    if 'This story was generated by' in text_to_match:
        return('1')
    elif 'This story includes elements generated' in text_to_match:
        return('2')
    elif 'Elements of this story were generated' in text_to_match:
        return('2')
    elif 'Portions of this story were generated' in text_to_match:
        return('2')
    elif 'Parts of this story were generated' in text_to_match:
        return('2')
    elif 'A portion of this story was generated' in text_to_match:
        return('2')
    elif 'This sory was partially generated by' in text_to_match:
        return('2')
    elif 'This story contains elements generated by' in text_to_match:
        return('2')
    elif 'This story includes information generated by' in text_to_match:
        return('2')
    elif 'This story was originally generated by' in text_to_match:
        return('1')
    else:
        return('3')


def extract_data(filename):
    with open(filename, 'r') as file1:
        text1=file1.read()
#locate the date of the article
    matches = list(datefinder.find_dates(text1))
    if len(matches) > 0:
        date=matches[1]
        strdate = str(date)
    else:
        print 'No dates found'



#locate the name of the company2
    matchcomp2 = text1.split(' ', 1)[0]
#count the number of words in the article
    matchcount = re.search(r'(.*) words', text1).group(1).strip()
#determine the article
    matchw =str(matchwho(text1))
#list the returns in a line
    combid = matchcomp2 + "," + strdate + "," + matchw + "," + matchcount
#save in txt format
    with open('outfile.txt', "a+") as outfile:
        outfile.write("\n"+combid)

files = os.listdir("C:\Users\dul\Dropbox\Article\parsedarticles")
for file in files:
    if ".txt" in file:
        extract_data(file)

Answer 1

strdate仅在len（matches）> 0的情况下定义，但在分配给combid的任何情况下都使用。

Answer 2

This fails when len(matches) < 0

def extract_data(filename):
...
    if len(matches) > 0:
        date=matches[1]
        strdate = str(date)
    else:
        print 'No dates found'

So if your conditional statement fails, strdate never gets set. However,

combid = matchcomp2 + "," + strdate + "," + matchw + "," + matchcount

is dependent on that being set and assumes it will always be set.

Based on what you want to achieve there is several things you can do. One such example is this.

def extract_data(filename):
...
    if len(matches) > 0:
        date=matches[1]
        strdate = str(date)
    else:
        print 'No dates found in {}'.format(filename)
        strdate = ''

Answer 3

Looks like you are assigning strdate only when the len(matches) > 0 predicate is true, try to add a default strdate value either at the beginning or inside else clause to debug if that is the case.

It seems you are trying to call strdate but because the if condition is not true the code doesn't know what strdate is (since it hasnt been assigned yet due to the if statement being false).

That's my guess.