为什么我会收到带有以下代码的 NameError？答案

【问题标题】：Why am I getting a NameError with below code?为什么我会收到带有以下代码的 NameError？
【发布时间】：2021-07-06 12:08:44
【问题描述】：

code error message

我收到变量 data_A 的名称错误，我不知道为什么...感谢任何帮助。谢谢！关注的变量是data_A

import sys
import csv
import statistics
#modularizing week1 program
def main():

    try:
        column = int(sys.argv[1])
        filename = sys.argv[2]
        with open(filename,'r') as csv_file:
            csv_x = csv.reader(csv_file, delimiter=' ', skipinitialspace=True)
            data_A = [float(line[column-1]) for line in csv_x if (float(line[column-1]))!=-9999.0]
    except:
        column = int(sys.argv[1])
        csv_x = csv.reader(sys.stdin, delimiter= ' ', skipinitialspace=True)
        data_A = [float(line[column-1]) for line in csv_x if (float(line[column-1]))!=-9999.0]

#statistical analysis for data
print(
    'min:', min(data_A),
    'max:', max(data_A),
    ', average:', mean(data_A),
    ', median:', median(data_A)
)

def compute_stats(values):
    import statistics

    if values == []:
        return(None,None,None,None)
    else:
        minimum = min(values)
        maximum = max(values)
        mean = statistics.mean(values)
        median = statistics.median(values)
        return(minimum,maximum,mean,median)

#call main function if code is not working
if __name__ == "__main__":
    main()

【问题讨论】：

标签： csv error-handling nameerror sos

【解决方案1】：

您收到名称错误，因为“data_A”的范围在封闭方法内，即 main()。因此，“data_A”在 main() 之外是不可见的。

避免这种情况的一种方法是将 print() 移到 main() 中

例如

def main():
    try:
        data_A = "localized"
    except Exception as e_x:
        data_A = "exception"

print(data_A)

if __name__ == "__main__":
    main()

Traceback (most recent call last):
  File "<string>", line 9, in <module>
NameError: name 'data_A' is not defined

在 main() 中移动 print 解析，例如

def main():
    try:
        data_A = "localized"
    except Exception as e_x:
        data_A = "exception"

    print(data_A)

if __name__ == "__main__":
    main()


> localized

【讨论】：