使用 Python (CSV Reader) 限制行号

Question

我想在下面的 python 代码中限制行数，如果行数少于 200 行则执行代码，如果行数多于 200 则 nit 运行代码。使用下面的代码，我正在打印行数，但是用于限制行的 if 子句给我错误。

TypeError: The view function did not return a valid response. The function either returned None or ended without a return statement.

ERROR:index:Exception on /CreateStudent[GET]

What i see in the browser: The server encountered an internal error and was unable to complete your request. Either the server is overloaded or there is an error in the application.

@app.route('/CreateStudent', methods=['GET','POST'])
    def upload_student():
        
       if request.method == 'POST':
            csv_file = request.files['file']
            if not csv_file:
                return render_template('error.html')
            csv_file = TextIOWrapper(csv_file, encoding='utf-8')
            csv_reader = csv.reader(csv_file)
            lines= list(csv_reader)
            print(lines)
            if len(lines) < 200:
                for row in lines:
                    if len(row)==4:
                        name=row[0]
                        familyname=row[1]
                        age=row[2]
                        job=row[3]
                        create_student(name,familyname,age,job)
                        time.sleep(2)
                return render_template('success.html')
            return render_template('CreateStudent.html')

当我还想只打印行时，我看到的结果如下： [['Sara','Jacky','22','engineer']] 为什么我的结果中有这个 2 [[]]，是因为列表吗？

Answer 1

这里我稍微修改了你的代码，并在我修改的地方添加了注释：

if request.method == 'POST':
    csv_file = request.files['file']
    if not csv_file:
        return render_template('error.html')
    csv_file = TextIOWrapper(csv_file, encoding='utf-8')
    csv_reader = csv.reader(csv_file)
    lines = list(csv_reader)            # <--- read the file into `lines`

    if len(lines) < 200:
        for row in lines:               # <-- we're iterating over `lines` now
            if len(row)==4:
                create_Student(*row)    # <-- no need to extract to variables, simple `*` is enough
        return render_template('success.html')

    return render_template('CreateStudent.html')    # <-- this is returned in case len(lines) >= 200

使用 Python (CSV Reader) 限制行号

Limiting row numbers with Python (CSV Reader)

python

row

list

python-3.x

csvreader