python - unboundLocalError - 变量是字典中的关键

Question

def create_school(school,year):
    all_students = {}
    achievements= {}
    var = data.Files.get(school,year)
    for child in var.student_info_parsed:
        for gchild in var.student_info_parsed[child]:
            for ggchild in var.student_info_parsed[child][gchild]:
                all_students[ggchild[0]] = ggchild
    for child in var.student_info:
        for gchild in var.student_info[child]:
            if gchild == 'localidentifier':
                student = var.student_info[child][gchild]
                achievements[student] = {}
                achievements[student]['certificates'] = []
                achievements[student]['otherachievements'] = []
            if gchild == 'certificates':
                for ggchild in var.student_info[child][gchild]:
                    cert = var.student_info[child][gchild][ggchild]
                    cert_year = cert[2][0:4]
                    if cert_year == year:
                        achievements[student]['certificates'].append(cert)
            if gchild == 'otherachievements':
                ocert = var.student_info[child][gchild]
                n = 0
                while n < len(ocert):
                    ocert_year = ocert[n][1]
                    if ocert_year == year:
                        achievements[student]['otherachievements'].append(ocert[n])
                    n = n+1
            if gchild == 'endorsements':
                ecert = var.student_info[child][gchild]
                l = list()
                for subj in ecert:
                    if ecert[subj]['courseendorsementresult'] != 'NO':
                        result = ecert[subj]['courseendorsementresult']
                        l.append([subj,result]) 
                achievements[student]['endorsements'] = l
    return achievements

所以在我添加条件之前

if gchild == 'endorsements':
    ecert = var.student_info[child][gchild]
    l = list()
    for subj in ecert:
        if ecert[subj]['courseendorsementresult'] != 'NO':
        result = ecert[subj]['courseendorsementresult']
            l.append([subj,result]) 
    achievements[student]['endorsements'] = l

一切都会找到，但现在我遇到了错误

  File "/Users/Teacher/Documents/Python/Standards/Data_Manipulation_3/data_man.py", line 454, in create_school
    achievements[student]['endorsements'] = l
UnboundLocalError: local variable 'student' referenced before assignment

对我来说奇怪的是到目前为止我一直在引用“学生”。

我没有名为student的全局变量？

我真的很困惑，我认为这些错误是在全局变量和局部变量之间存在混淆但“学生”变量只是局部变量时发生的？

任何帮助将不胜感激。

Answer 1

您的变量 student 是在 if gchild == 'localidentifier' 前面的 block 中创建的。如果执行该 block ，变量 student 将可用。但是，如果 if gchild == 'endorsements' 前面的 block 在另一个 block 之前执行(因为 gchild=='endorsements'早于 gchild=='localidentifier' 的迭代)，那么变量 student 将不会被创建。