第14篇：其他

相关配置

本节介绍一些对 Pandas 的全局性的配置和设置，可以节省我们在使用过程中的一些重复操作。

信息显示

显示版本号：

pd.__version__
# '1.2.0'

显示依赖包的安装情况和版本号：

pd.show_versions()

配置操作

# 显示最大行数（默认60）
pd.get_option("display.max_rows")
pd.options.display.max_rows
# 60

# 设置最大行数
pd.set_option("display.max_rows", 999)
pd.options.display.max_rows = 999

# 重置为默认
pd.reset_option("display.max_rows")

# 浮点数字格式
pd.set_option("display.float_format", "{:.20f}".format)

常用操作

操作	默认值	功能
display.chop_threshold	None	If set to a float value, all float values smaller then the given threshold will be displayed as exactly 0 by repr and friends.
display.colheader_justify	right	Controls the justification of column headers. used by DataFrameFormatter.
display.column_space	12	No description available.
display.date_dayfirst	FALSE	When True, prints and parses dates with the day first, eg 20/01/2005
display.date_yearfirst	FALSE	When True, prints and parses dates with the year first, eg 2005/01/20
display.encoding	UTF-8	Defaults to the detected encoding of the console. Specifies the encoding to be used for strings returned by to_string, these are generally strings meant to be displayed on the console.
display.expand_frame_repr	TRUE	Whether to print out the full DataFrame repr for wide DataFrames across multiple lines, max_columns is still respected, but the output will wrap-around across multiple “pages” if its width exceeds display.width.
display.float_format	None	The callable should accept a floating point number and return a string with the desired format of the number. This is used in some places like SeriesFormatter. See core.format.EngFormatter for an example.
display.large_repr	truncate	For DataFrames exceeding max_rows/max_cols, the repr (and HTML repr) can show a truncated table (the default), or switch to the view from df.info() (the behaviour in earlier versions of pandas). allowable settings, [‘truncate’, ‘info’]
display.latex.repr	FALSE	Whether to produce a latex DataFrame representation for jupyter frontends that support it.
display.latex.escape	TRUE	Escapes special characters in DataFrames, when using the to_latex method.
display.latex.longtable	FALSE	Specifies if the to_latex method of a DataFrame uses the longtable format.
display.latex.multicolumn	TRUE	Combines columns when using a MultiIndex
display.latex.multicolumn_format	‘l’	Alignment of multicolumn labels
display.latex.multirow	FALSE	Combines rows when using a MultiIndex. Centered instead of top-aligned, separated by clines.
display.max_columns	0 or 20	max_rows and max_columns are used in repr() methods to decide if to_string() or info() is used to render an object to a string. In case Python/IPython is running in a terminal this is set to 0 by default and pandas will correctly auto-detect the width of the terminal and switch to a smaller format in case all columns would not fit vertically. The IPython notebook, IPython qtconsole, or IDLE do not run in a terminal and hence it is not possible to do correct auto-detection, in which case the default is set to 20. ‘None’ value means unlimited.
display.max_colwidth	50	The maximum width in characters of a column in the repr of a pandas data structure. When the column overflows, a “…” placeholder is embedded in the output. ‘None’ value means unlimited.
display.max_info_columns	100	max_info_columns is used in DataFrame.info method to decide if per column information will be printed.
display.max_info_rows	1690785	df.info() will usually show null-counts for each column. For large frames this can be quite slow. max_info_rows and max_info_cols limit this null check only to frames with smaller dimensions then specified.
display.max_rows	60	This sets the maximum number of rows pandas should output when printing out various output. For example, this value determines whether the repr() for a dataframe prints out fully or just a truncated or summary repr. ‘None’ value means unlimited.
display.min_rows	10	The numbers of rows to show in a truncated repr (when max_rows is exceeded). Ignored when max_rows is set to None or 0. When set to None, follows the value of max_rows.
display.max_seq_items	100	when pretty-printing a long sequence, no more then max_seq_items will be printed. If items are omitted, they will be denoted by the addition of “…” to the resulting string. If set to None, the number of items to be printed is unlimited.
display.memory_usage	TRUE	This specifies if the memory usage of a DataFrame should be displayed when the df.info() method is invoked.
display.multi_sparse	TRUE	“Sparsify” MultiIndex display (don’t display repeated elements in outer levels within groups)
display.notebook_repr_html	TRUE	When True, IPython notebook will use html representation for pandas objects (if it is available).
display.pprint_nest_depth	3	Controls the number of nested levels to process when pretty-printing
display.precision	6	Floating point output precision in terms of number of places after the decimal, for regular formatting as well as scientific notation. Similar to numpy’s precision print option
display.show_dimensions	truncate	Whether to print out dimensions at the end of DataFrame repr. If ‘truncate’ is specified, only print out the dimensions if the frame is truncated (e.g. not display all rows and/or columns)
display.width	80	Width of the display in characters. In case python/IPython is running in a terminal this can be set to None and pandas will correctly auto-detect the width. Note that the IPython notebook, IPython qtconsole, or IDLE do not run in a terminal and hence it is not possible to correctly detect the width.
display.html.table_schema	FALSE	Whether to publish a Table Schema representation for frontends that support it.
display.html.border	1	A border=value attribute is inserted in the <table> tag for the DataFrame HTML repr.
display.html.use_mathjax	TRUE	When True, Jupyter notebook will process table contents using MathJax, rendering mathematical expressions enclosed by the dollar symbol.
io.excel.xls.writer	xlwt	The default Excel writer engine for ‘xls’ files.
io.excel.xlsm.writer	openpyxl	The default Excel writer engine for ‘xlsm’ files. Available options: ‘openpyxl’ (the default).
io.excel.xlsx.writer	openpyxl	The default Excel writer engine for ‘xlsx’ files.
io.hdf.default_format	None	default format writing format, if None, then put will default to ‘fixed’ and append will default to ‘table’
io.hdf.dropna_table	TRUE	drop ALL nan rows when appending to a table
io.parquet.engine	None	The engine to use as a default for parquet reading and writing. If None then try ‘pyarrow’ and ‘fastparquet’
mode.chained_assignment	warn	Controls SettingWithCopyWarning: ‘raise’, ‘warn’, or None. Raise an exception, warn, or no action if trying to use chained assignment.
mode.sim_interactive	FALSE	Whether to simulate interactive mode for purposes of testing.
mode.use_inf_as_na	FALSE	True means treat None, NaN, -INF, INF as NA (old way), False means None and NaN are null, but INF, -INF are not NA (new way).
compute.use_bottleneck	TRUE	Use the bottleneck library to accelerate computation if it is installed.
compute.use_numexpr	TRUE	Use the numexpr library to accelerate computation if it is installed.
plotting.backend	matplotlib	Change the plotting backend to a different backend than the current matplotlib one. Backends can be implemented as third-party libraries implementing the pandas plotting API. They can use other plotting libraries like Bokeh, Altair, etc.
plotting.matplotlib.register_converters	TRUE	Register custom converters with matplotlib. Set to False to de-register.

https://pandas.pydata.org/docs/user_guide/options.html

在代码编写过程和程序运行时，Pandas 会抛出一些异常。本页介绍 Pandas 的异常定义和处理方法， 同时收集 Pandas 常见的错误，并分析其可能的原因。

异常和警告及常见错误

在代码编写过程和程序运行时，Pandas 会抛出一些异常。本页介绍 Pandas 的异常定义和处理方法， 同时收集 Pandas 常见的错误，并分析其可能的原因。

异常和警告

在pandas中常见的异常和警告对象有：

• 访问器注册中的属性冲突警告 pandas.errors.AccessorRegistrationWarning
• 数据类型警告 pandas.errors.DtypeWarning
• 空数据错误 pandas.errors.EmptyDataError
• 无效索引错误 pandas.errors.InvalidIndexError
• 合并错误 pandas.errors.MergeError
• 空频率错误 pandas.errors.NullFrequencyError
• 数字错误 pandas.errors.NumbaUtilError
• 时间出界 pandas.errors.OutOfBoundsDatetime
• 时长超界 pandas.errors.OutOfBoundsTimedelta
• 分析器错误 pandas.errors.ParserError
• 分析器警告 pandas.errors.ParserWarning
• 性能预警 pandas.errors.PerformanceWarning
• 非排序索引错误 pandas.errors.UnsortedIndexError
• 不支持的函数调用 pandas.errors.UnsupportedFunctionCall

常见异常

ValueError

'''
ValueError: The truth value of a Series is ambiguous.
Use a.empty, a.bool(), a.item(), a.any() or a.all().
'''

以上错误一般是返回一了一个布尔序列，解决办法有：

• 设定轴的方法，一般是 axis=1
• 按提示给出 a.any() or a.all() 让其返回一个固定值

'''
ValueError: Length mismatch: Expected axis has 6 elements,
new values have 7 elements
'''

以上错误是设定的数据长度与原数据长度不匹配，比如有6列设置了7个列名，有6条数据，但修改时给出7条数据等等。

InvalidIndexError

'''
InvalidIndexError: Reindexing only valid with uniquely
valued Index objects
'''

以上错误如果是使用 pd.concat() 发生的，原因是两个 DataFrame 索引不相同，需要对他们分别重新设置索引 df.reset_index('X')。

TypeError

'''
TypeError: '<' not supported between instances of 'float' and 'str'
'''

以上错误是由于两个列中其中一个字符型，不能与另外一个浮点型做比较运算，此时需要将其先转为数字类型再计算。