Python之Pandas：pandas.DataFrame.to_csv函数的简介、具体案例、使用方法详细攻略

def to_csv Found at: pandas.core.generic

def to_csv(
self,
path_or_buf:Optional[FilePathOrBuffer]=None,
sep:str=”,”,
na_rep:str=””,
float_format:Optional[str]=None,
columns:Optional[Sequence[Label]]=None,
header:Union[bool_tList[str]]=True,
index:bool_t=True,
index_label:Optional[Union[bool_tstrSequence[Label]]]
=None,
mode:str=”w”,
encoding:Optional[str]=None,
compression:Optional[Union[strMapping[strstr]]]=”infer”,
quoting:Optional[int]=None,
quotechar:str='”‘,
line_terminator:Optional[str]=None,
chunksize:Optional[int]=None,
date_format:Optional[str]=None,
doublequote:bool_t=True,
escapechar:Optional[str]=None,
decimal:Optional[str]=”.”,
errors:str=”strict”)->
Optional[str]:
r”””
Write object to a comma-separated values (csv) file.

.. versionchanged:: 0.24.0
The order of arguments for Series was changed.

Parameters
———-
path_or_buf : str or file handle, default None. File path or object, if None is provided the result is returnedas a string. If a file object is passed it should be opened with `newline=”`, disabling universal newlines.
.. versionchanged:: 0.24.0
Was previously named “path” for Series.

sep : str, default ‘,’. String of length 1. Field delimiter for the output file.
na_rep : str, default ”. Missing data representation.
float_format : str, default None. Format string for floating point numbers.
columns : sequence, optional. Columns to write.
header : bool or list of str, default True.Write out the column names. If a list of strings is given it is assumed to be aliases for the column names.
.. versionchanged:: 0.24.0
Previously defaulted to False for Series.

index : bool, default True. Write row names (index).
index_label : str or sequence, or False, default None. Column label for index column(s) if desired. If None is given, and `header` and `index` are True, then the index names are used. A sequence should be given if the object uses MultiIndex. IfFalse do not print fields for index names. Useindex_label=False for easier importing in R.
mode : str.Python write mode, default ‘w’.
encoding : str, optional.A string representing the encoding to use in the output file, defaults to ‘utf-8’.
compression : str or dict, default ‘infer’. If str, represents compression mode. If dict, value at ‘method’ isthe compression mode. Compression mode may be any ofthe following
possible values: {‘infer’, ‘gzip’, ‘bz2’, ‘zip’, ‘xz’, None}. If compression mode is ‘infer’ and `path_or_buf` is path-like,then detect compression mode from the following extensions: ‘. gz’, ‘.bz2’, ‘.zip’ or ‘.xz’. (otherwise no compression). If dict givenand mode is one of {‘zip’, ‘gzip’, ‘bz2’}, or inferred as one of the above, other entries passed as additional compression options.

.. versionchanged:: 1.0.0
May now be a dict with key ‘method’ as compression mode and other entries as additional compression options if compression mode is ‘zip’.
.. versionchanged:: 1.1.0
Passing compression options as keys in dict issupported for compression modes ‘gzip’ and ‘bz2’as well as ‘zip’.

参数
———-
path_or_buf :str或file handle，默认无。文件路径或对象，如果没有提供，结果将作为字符串返回。如果一个文件对象被传递，它应该被打开’ newline= ” ‘，禁用通用换行。
. .versionchanged: 0.24.0
之前被命名为“path”系列。

sep : str，默认为’，’。长度为1的字符串。输出文件的字段分隔符。
na_rep : str，默认值”。缺失的数据表示。
float_format :str，默认没有。浮点数的格式字符串。
columns :序列，可选。列写。
header :bool或str列表，默认为True。写出列名。如果给定了字符串列表，则假定它是列名的别名。
. .versionchanged: 0.24.0
以前对于级数默认为False。

index :bool，默认为True。写行名称(索引)。

• cats_df_temp.to_csv(cats_csv_file,index=None)   #输出不加默认的索引列

iindex_label : str或序列，或False，默认无。如果需要，用于索引列的列标签。如果没有给出，并且’ header ‘和’ index ‘为真，则使用索引名。如果对象使用多索引，则应该给出一个序列。如果为False，不要打印索引名称的字段。使用index_label=False在R中更容易导入。
mode :str.Python编写模式，默认为“w”。
encoding :str，可选。表示要在输出文件中使用的编码的字符串，默认为“utf-8”。
compression :str或dict，默认为’infer’。如果为str，表示压缩模式。如果是dict, value at ‘method’是压缩模式。压缩模式可以是下列任何一种
possible values: {‘infer’, ‘gzip’, ‘bz2’, ‘zip’, ‘xz’, None}.。如果压缩模式是’infer’，而’ path_or_buf ‘是类似路径的，那么从以下扩展中检测压缩模式:’。 ‘. gz’, ‘.bz2’, ‘.zip’ or ‘.xz’. 。(否则不压缩)。如果dict given和mode是{‘zip’、’gzip’、’bz2’}或推断为上述选项之一，则其他项作为附加压缩选项传递。

. .versionchanged: 1.0.0
如果压缩模式是“zip”，则可以使用关键的“方法”作为压缩模式，其他条目作为附加的压缩选项。
. .versionchanged: 1.1.0
压缩模式“gzip”和“bz2”以及“zip”支持将压缩选项作为键在dict中传递。

quoting : optional constant from csv module. Defaults to csv.QUOTE_MINIMAL. If you have set a `float_format` then floats are converted to strings and thus csv. QUOTE_NONNUMERIC will treat them as non-numeric.
quotechar : str, default ‘\”‘. String of length 1. Character used to quote fields.
line_terminator : str, optional. The newline character or character sequence to use in the output file. Defaults to `os.linesep`, which depends on the OS in which this method is called (‘\n’ for linux, ‘\r\n’ for Windows, i.e.).
.. versionchanged:: 0.24.0
chunksize : int or None. Rows to write at a time.
date_format : str, default None.Format string for datetime objects.
doublequote : bool, default True. Control quoting of `quotechar` inside a field.
escapechar : str, default None. String of length 1. Character used to escape `sep` and `quotechar` when appropriate.
decimal : str, default ‘.’. Character recognized as decimal separator. E.g. use ‘,’ for European data.
errors : str, default ‘strict’.Specifies how encoding and decoding errors are to behandled. See the errors argument for :func:`open` for a full list of options.
.. versionadded:: 1.1.0

另请参阅
 ——–
read_csv:将CSV文件加载到一个DataFrame中。
to_excel:将DataFrame写入Excel文件。

Examples
——–
>>> df = pd.DataFrame({‘name’: [‘Raphael’, ‘Donatello’],
… ‘mask’: [‘red’, ‘purple’],
… ‘weapon’: [‘sai’, ‘bo staff’]})
>>> df.to_csv(index=False)
‘name,mask,weapon\nRaphael,red,sai\nDonatello,purple,bo
staff\n’

Create ‘out.zip’ containing ‘out.csv’

>>> compression_opts = dict(method=’zip’,
… archive_name=’out.csv’) # doctest: +SKIP
>>> df.to_csv(‘out.zip’, index=False,
… compression=compression_opts) # doctest: +SKIP
“””
df = self if isinstance(self, ABCDataFrame) else self.to_frame()
from pandas.io.formats.csvs import CSVFormatter
formatter = CSVFormatter(
df,
path_or_buf,
line_terminator=line_terminator,
sep=sep,
encoding=encoding,
errors=errors,
compression=compression,
quoting=quoting,
na_rep=na_rep,
float_format=float_format,
cols=columns,
header=header,
index=index,
index_label=index_label,
mode=mode,
chunksize=chunksize,
quotechar=quotechar,
date_format=date_format,
doublequote=doublequote,
escapechar=escapechar,
decimal=decimal)
formatter.save()
if path_or_buf is None:
return formatter.path_or_buf.getvalue()
return None

# ———————————————————————-
# Lookup Caching