python - 类型错误 : 'int' object is not iterable in python

Question

def export_csv_standard_units(name):
    cursor.execute("select distinct(standard_units) from activities where standard_type='IC50' ")
    result_standard_units_distinct = cursor.fetchall()

    cursor.execute("select standard_units from activities where standard_type='IC50' ")
    result_standard_units = cursor.fetchall()

    field_standard_units = ()
    cnt = []

    for result in result_standard_units_distinct:
        field_standard_units = field_standard_units + (result_standard_units_distinct,)

    length = int(len(field_standard_units))

    for i in result_standard_units:
        for j in length:
            if field_standard_units(j) == result_standard_units(9):
                cnt[j] = cnt[j] + 1
    field = (field_standard_units, cnt)

    export_field = open('%s_standard_units.csv' %name, 'wb')
    export_csv_field = csv.writer(export_field)
    export_csv_field.writerows([field])

    export_field.close()

我在运行 python 文件时遇到一些问题。我想制作 csv.file 用于数据计数像这样..

standard_units 计数标准单元1 123标准单元2 234

但是，它有这样的错误。

   File "manage.py", line 42
     for j in length:
   TypeError: 'int' object is not iterable

可迭代是什么意思？

Answer 1

就像你的错误消息所说:ints 是不可迭代的。使用range

for j in range(length):
    ...

如果length为10，range(length)将为您提供值0..9。

您不必提前实际计算长度 - 相反，您可以 enumerate field_standard_units:

for j, unit in enumerate(field_standard_units):
    if unit == result_standard_units(9):  # What's 9?
        ...

注意:使用xrange如果您的范围非常大，因为 range 创建了一个列表，因此它的所有成员都占用了内存，而 xrange 创建了一个生成器，就像 enumerate >.