汇编.csv文件以创建一个大的.csv将列的数据类型更改为“object”

Question

我正在为我的项目使用pycharm，pandas框架和python 3.3。我最初有200个.csv.gz文件，我想从中创建一个大的.csv文件。下面是它的代码，它正在运行

import gzip
import csv
import glob
import os

pathname=os.path.expanduser("~/Desktop/downloaded/*.csv.gz")
path=os.path.expanduser("~/Desktop/downloaded")
#path = pathname+"/*.csv.gz" #folder containing all .csv.gz files
counter = 1 #counts total number of files read
files = glob.glob(pathname)
try:
    for file in files:  # read files one by one
        with gzip.open(file,'rt',encoding="utf-8",errors="ignore") as mycsvread:
            filecontent = csv.reader(mycsvread)
            if counter > 1:
                header = mycsvread.readline()  # skip header file
            with open(path+"/combinedcsv.csv", 'a') as mycsvwrite:
                datawriter = csv.writer(mycsvwrite)
                for row in filecontent:
                    datawriter.writerow(row)
except IOError:
    print("File not found")
except EOFError:
    print("No input")
else:
    counter = counter + 1

但问题是所有列都被转换为“object”数据类型。当我创建数据帧并将大的.csv文件读入其中时，我发现了这一点。这是dataframe.dtypes输出：

 BEGIN_YEARMONTH       object
    BEGIN_DAY             object
    BEGIN_TIME            object
    END_YEARMONTH         object
    END_DAY               object
    END_TIME              object
    EPISODE_ID            object
    EVENT_ID              object
    STATE                 object
    STATE_FIPS            object
    YEAR                  object
    MONTH_NAME            object
    EVENT_TYPE            object
    CZ_TYPE               object
    CZ_FIPS               object
    CZ_NAME               object
    WFO                   object
    BEGIN_DATE_TIME       object
    CZ_TIMEZONE           object
    END_DATE_TIME         object
    INJURIES_DIRECT       object
    INJURIES_INDIRECT     object

请告诉我保留原始数据类型的列吗？