python 中的变量赋值错误

Question

我得到了一个变量赋值错误，显然没有理解一些东西，但从我的代码中，我不明白为什么会发生这种情况。代码：   def something(filename):    with open("tmp/"+filename.stem+".txt", "r") as infile: # opening the tmp file for scraping the data        readfile = infile.readlines() #reads the infile lne by line and returns a list containing the lines        for i, line in enumerate(readfile[1:], 1): # looping over all the lines in the file from position 1 (so skipping 0) to avoid circular feedback            if 'Overview' in line:                start = i                continue                for i, line in enumerate(readfile[1:], 1):                    if 'Identified secondary metabolite regions using strictness' in line:                        end = i                        marker = list(map(lambda s: s.strip('\n'), readfile[start + 1:end])) # stripping the '\n' off every element in the list. map executes a function for each element in a sequence        for i, line in enumerate(readfile[1:], 1): # looping over all the lines in the file from position 1 (so skipping 0) to avoid circular feedback            for location in marker:错误：UnboundLocalError: local variable 'marker' referenced before assignment由于第一个 forloop 在第二个 forloop 之前执行导致被设置，因此不应始终在函数范围内进行赋值？markermarker其次，使用两个for循环似乎很混乱，我如何在一个for循环中执行此操作？

Answer 1

关键是，它是在“如果”条件下分配的。如果它是假的呢？marker




Answer 2

尝试在函数外部定义标记变量。然后在功能中使用它。

refer-> 不明白为什么 UnboundLocalError 会发生

Answer 3

marker在不满足条件时未设置。设置在开头。if 'Identified secondary metabolite regions using strictness' in line:marker = []