所以我正在读取来自 NOAA 的站点代码 csv 文件，如下所示:

"USAF","WBAN","STATION NAME","CTRY","FIPS","STATE","CALL","LAT","LON","ELEV(.1M)","BEGIN","END"
"006852","99999","SENT","SW","SZ","","","+46817","+010350","+14200","",""
"007005","99999","CWOS 07005","","","","","-99999","-999999","-99999","20120127","20120127"

前两列包含气象站的代码，有时它们有前导零。当 pandas 在不指定数据类型的情况下导入它们时，它们会变成整数。这没什么大不了的，因为我可以遍历数据帧索引并将它们替换为 "%06d"% i 之类的东西，因为它们始终是六位数，但你知道......这就是懒惰的人的方式。

使用此代码获取 csv:

file = urllib.urlopen(r"ftp://ftp.ncdc.noaa.gov/pub/data/inventories/ISH-HISTORY.CSV")
output = open('Station Codes.csv','wb')
output.write(file.read())
output.close()

这一切都很好，但是当我去尝试使用它阅读它时:

import pandas as pd
df = pd.io.parsers.read_csv("Station Codes.csv",dtype={'USAF': np.str, 'WBAN': np.str})

或

import pandas as pd
df = pd.io.parsers.read_csv("Station Codes.csv",dtype={'USAF': str, 'WBAN': str})

我收到一条讨厌的错误消息:

File "C:\Python27\lib\site-packages\pandas-0.11.0-py2.7-win32.egg\pandas\io\parsers.py", line 401, in parser
_f
    return _read(filepath_or_buffer, kwds)
  File "C:\Python27\lib\site-packages\pandas-0.11.0-py2.7-win32.egg\pandas\io\parsers.py", line 216, in _read
    return parser.read()
  File "C:\Python27\lib\site-packages\pandas-0.11.0-py2.7-win32.egg\pandas\io\parsers.py", line 633, in read
    ret = self._engine.read(nrows)
  File "C:\Python27\lib\site-packages\pandas-0.11.0-py2.7-win32.egg\pandas\io\parsers.py", line 957, in read
    data = self._reader.read(nrows)
  File "parser.pyx", line 654, in pandas._parser.TextReader.read (pandas\src\parser.c:5931)
  File "parser.pyx", line 676, in pandas._parser.TextReader._read_low_memory (pandas\src\parser.c:6148)
  File "parser.pyx", line 752, in pandas._parser.TextReader._read_rows (pandas\src\parser.c:6962)
  File "parser.pyx", line 837, in pandas._parser.TextReader._convert_column_data (pandas\src\parser.c:7898)
  File "parser.pyx", line 887, in pandas._parser.TextReader._convert_tokens (pandas\src\parser.c:8483)
  File "parser.pyx", line 953, in pandas._parser.TextReader._convert_with_dtype (pandas\src\parser.c:9535)
  File "parser.pyx", line 1283, in pandas._parser._to_fw_string (pandas\src\parser.c:14616)
TypeError: data type not understood

这是一个相当大的 csv(31k 行)所以也许这与它有关？

最佳答案

这是pandas dtype guessing的问题。

Pandas 看到数字并猜测您希望它是数字。

为了让 pandas 不怀疑你的意图，你应该设置你想要的数据类型:object

pd.read_csv('filename.csv', dtype={'leading_zero_column_name': object})

会成功的

更新，因为它可以帮助其他人:

要将所有列作为str，可以这样做(来自评论):

pd.read_csv('sample.csv', dtype = str)

要将大多数或选择性列作为str，可以这样做:

# lst of column names which needs to be string
lst_str_cols = ['prefix', 'serial']
# use dictionary comprehension to make dict of dtypes
dict_dtypes = {x : 'str'  for x in lst_str_cols}
# use dict on dtypes
pd.read_csv('sample.csv', dtype=dict_dtypes)

关于python - Pandas read_csv dtype 前导零，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/16929056/