python写入csv中文乱码问题，encoding='utf-8'无效还是乱码——吕江民·日常随笔

今天在处理python写入csv中文乱码问题，尝试各种办法，百思不得其解，网上找到的最常用的办法就是

1. encoding='utf-8'：无效

with open('data4.csv', 'a', encoding='utf-8', newline='') as csvfile:
    fieldnames = (['id', 'name', 'age'])
    writer = csv.DictWriter(csvfile, fieldnames=fieldnames)
    writer.writerow({'id': '10005', 'name': '张伟', 'age': '32'})

2. encoding='utf-8-sig'：有效

with open(filename, 'a', newline='', encoding='utf-8-sig') as f: # 中文需要设置成utf-8格式
    f_csv = csv.writer(f)
    f_csv.writerow(('城市', '日期', '天气', '风力', '温度', '摄氏度')) # 头部信息
    f_csv.writerows(data)

3. 先转码再储存：无效

data.decode('utf-8').encode('gbk')

4. 甚至直接以gbk编码写入：无效

f = codecs.open("xx.csv", 'wb', "gbk")
writer = csv.writer(f)
writer.writerow(["客户名称", "行业类型", "客户联系人", "职位", "联系方式", "邮箱","地址"])

到此为止，中文还是乱码，我甚至开始怀疑我的excel软件是不是坏了，。
WPS：想什么呢，我糖糖WPS怎么可能让你随便转换编码，我又不是Notepad++，我是高贵的office！

打开csv源码发现dialect="excel"

反思一下，是不是因为csv太Low了，于是竟然成功了！！！丝毫不敢代码，赶紧贴出来，以防还有新手朋友摆渡摆到翻船。拿走不谢...

writer = csv.DictWriter(csvfile, fieldnames=fieldnames, dialect="excel")

贴上源码：

class DictWriter:
    def __init__(self, f, fieldnames, restval="", extrasaction="raise",
                 dialect="excel", *args, **kwds):
        self.fieldnames = fieldnames    # list of keys for the dict
        self.restval = restval          # for writing short dicts
        if extrasaction.lower() not in ("raise", "ignore"):
            raise ValueError("extrasaction (%s) must be 'raise' or 'ignore'"
                             % extrasaction)
        self.extrasaction = extrasaction
        self.writer = writer(f, dialect, *args, **kwds)

    def writeheader(self):
        header = dict(zip(self.fieldnames, self.fieldnames))
        self.writerow(header)

    def _dict_to_list(self, rowdict):
        if self.extrasaction == "raise":
            wrong_fields = rowdict.keys() - self.fieldnames
            if wrong_fields:
                raise ValueError("dict contains fields not in fieldnames: "
                                 + ", ".join([repr(x) for x in wrong_fields]))
        return (rowdict.get(key, self.restval) for key in self.fieldnames)

    def writerow(self, rowdict):
        return self.writer.writerow(self._dict_to_list(rowdict))

    def writerows(self, rowdicts):
        return self.writer.writerows(map(self._dict_to_list, rowdicts))

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吃完饭回来发现是python缓存导致，其实encoding='utf-8-sig'是有效，但当时测了很多遍都没生效，缓存误国啊，dialect默认值就是"excel"，不需要修改。