python下的Pandas中DataFrame基本操作(一),基本函数整理

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简介

pandas作者Wes McKinney 在【PYTHON FOR DATA ANALYSIS】中对pandas的方方面面都有了一个权威简明的入门级的介绍,但在实际使用过程中,我发现书中的内容还只是冰山一角。谈到pandas数据的行更新、表合并等操作,一般用到的方法有concat、join、merge。但这三种方法对于很多新手来说,都不太好分清使用的场合与用途。

构造函数

方法描述
DataFrame([data, index, columns, dtype, copy])构造数据框

属性和数据

方法描述
Axesindex: row labels;columns: column labels
DataFrame.as_matrix([columns])转换为矩阵
DataFrame.dtypes返回数据的类型
DataFrame.ftypesReturn the ftypes (indication of sparse/dense and dtype) in this object.
DataFrame.get_dtype_counts()返回数据框数据类型的个数
DataFrame.get_ftype_counts()Return the counts of ftypes in this object.
DataFrame.select_dtypes([include, exclude])根据数据类型选取子数据框
DataFrame.valuesNumpy的展示方式
DataFrame.axes返回横纵坐标的标签名
DataFrame.ndim返回数据框的纬度
DataFrame.size返回数据框元素的个数
DataFrame.shape返回数据框的形状
DataFrame.memory_usage([index, deep])Memory usage of DataFrame columns.

类型转换

方法描述
DataFrame.astype(dtype[, copy, errors])转换数据类型
DataFrame.copy([deep])复制数据框
DataFrame.isnull()以布尔的方式返回空值
DataFrame.notnull()以布尔的方式返回非空值

索引和迭代

方法描述
DataFrame.head([n])返回前n行数据
DataFrame.at快速标签常量访问器
DataFrame.iat快速整型常量访问器
DataFrame.loc标签定位
DataFrame.iloc整型定位
DataFrame.insert(loc, column, value[, …])在特殊地点插入行
DataFrame.iter()Iterate over infor axis
DataFrame.iteritems()返回列名和序列的迭代器
DataFrame.iterrows()返回索引和序列的迭代器
DataFrame.itertuples([index, name])Iterate over DataFrame rows as namedtuples, with index value as first element of the tuple.
DataFrame.lookup(row_labels, col_labels)Label-based “fancy indexing” function for DataFrame.
DataFrame.pop(item)返回删除的项目
DataFrame.tail([n])返回最后n行
DataFrame.xs(key[, axis, level, drop_level])Returns a cross-section (row(s) or column(s)) from the Series/DataFrame.
DataFrame.isin(values)是否包含数据框中的元素
DataFrame.where(cond[, other, inplace, …])条件筛选
DataFrame.mask(cond[, other, inplace, axis, …])Return an object of same shape as self and whose corresponding entries are from self where cond is False and otherwise are from other.
DataFrame.query(expr[, inplace])Query the columns of a frame with a boolean expression.

二元运算

方法描述
DataFrame.add(other[, axis, level, fill_value])加法,元素指向
DataFrame.sub(other[, axis, level, fill_value])减法,元素指向
DataFrame.mul(other[, axis, level, fill_value])乘法,元素指向
DataFrame.div(other[, axis, level, fill_value])小数除法,元素指向
DataFrame.truediv(other[, axis, level, …])真除法,元素指向
DataFrame.floordiv(other[, axis, level, …])向下取整除法,元素指向
DataFrame.mod(other[, axis, level, fill_value])模运算,元素指向
DataFrame.pow(other[, axis, level, fill_value])幂运算,元素指向
DataFrame.radd(other[, axis, level, fill_value])右侧加法,元素指向
DataFrame.rsub(other[, axis, level, fill_value])右侧减法,元素指向
DataFrame.rmul(other[, axis, level, fill_value])右侧乘法,元素指向
DataFrame.rdiv(other[, axis, level, fill_value])右侧小数除法,元素指向
DataFrame.rtruediv(other[, axis, level, …])右侧真除法,元素指向
DataFrame.rfloordiv(other[, axis, level, …])右侧向下取整除法,元素指向
DataFrame.rmod(other[, axis, level, fill_value])右侧模运算,元素指向
DataFrame.rpow(other[, axis, level, fill_value])右侧幂运算,元素指向
DataFrame.lt(other[, axis, level])类似Array.lt
DataFrame.gt(other[, axis, level])类似Array.gt
DataFrame.le(other[, axis, level])类似Array.le
DataFrame.ge(other[, axis, level])类似Array.ge
DataFrame.ne(other[, axis, level])类似Array.ne
DataFrame.eq(other[, axis, level])类似Array.eq
DataFrame.combine(other, func[, fill_value, …])Add two DataFrame objects and do not propagate NaN values, so if for a
DataFrame.combine_first(other)Combine two DataFrame objects and default to non-null values in frame calling the method.

函数应用&分组&窗口

方法描述
DataFrame.apply(func[, axis, broadcast, …])应用函数
DataFrame.applymap(func)Apply a function to a DataFrame that is intended to operate elementwise, i.e.
DataFrame.aggregate(func[, axis])Aggregate using callable, string, dict, or list of string/callables
DataFrame.transform(func, *args, **kwargs)Call function producing a like-indexed NDFrame
DataFrame.groupby([by, axis, level, …])分组
DataFrame.rolling(window[, min_periods, …])滚动窗口
DataFrame.expanding([min_periods, freq, …])拓展窗口
DataFrame.ewm([com, span, halflife, alpha, …])指数权重窗口

描述统计学

方法描述
DataFrame.abs()返回绝对值
DataFrame.all([axis, bool_only, skipna, level])Return whether all elements are True over requested axis
DataFrame.any([axis, bool_only, skipna, level])Return whether any element is True over requested axis
DataFrame.clip([lower, upper, axis])Trim values at input threshold(s).
DataFrame.clip_lower(threshold[, axis])Return copy of the input with values below given value(s) truncated.
DataFrame.clip_upper(threshold[, axis])Return copy of input with values above given value(s) truncated.
DataFrame.corr([method, min_periods])返回本数据框成对列的相关性系数
DataFrame.corrwith(other[, axis, drop])返回不同数据框的相关性
DataFrame.count([axis, level, numeric_only])返回非空元素的个数
DataFrame.cov([min_periods])计算协方差
DataFrame.cummax([axis, skipna])Return cumulative max over requested axis.
DataFrame.cummin([axis, skipna])Return cumulative minimum over requested axis.
DataFrame.cumprod([axis, skipna])返回累积
DataFrame.cumsum([axis, skipna])返回累和
DataFrame.describe([percentiles, include, …])整体描述数据框
DataFrame.diff([periods, axis])1st discrete difference of object
DataFrame.eval(expr[, inplace])Evaluate an expression in the context of the calling DataFrame instance.
DataFrame.kurt([axis, skipna, level, …])返回无偏峰度Fisher’s (kurtosis of normal == 0.0).
DataFrame.mad([axis, skipna, level])返回偏差
DataFrame.max([axis, skipna, level, …])返回最大值
DataFrame.mean([axis, skipna, level, …])返回均值
DataFrame.median([axis, skipna, level, …])返回中位数
DataFrame.min([axis, skipna, level, …])返回最小值
DataFrame.mode([axis, numeric_only])返回众数
DataFrame.pct_change([periods, fill_method, …])返回百分比变化
DataFrame.prod([axis, skipna, level, …])返回连乘积
DataFrame.quantile([q, axis, numeric_only, …])返回分位数
DataFrame.rank([axis, method, numeric_only, …])返回数字的排序
DataFrame.round([decimals])Round a DataFrame to a variable number of decimal places.
DataFrame.sem([axis, skipna, level, ddof, …])返回无偏标准误
DataFrame.skew([axis, skipna, level, …])返回无偏偏度
DataFrame.sum([axis, skipna, level, …])求和
DataFrame.std([axis, skipna, level, ddof, …])返回标准误差
DataFrame.var([axis, skipna, level, ddof, …])返回无偏误差

从新索引&选取&标签操作

方法描述
DataFrame.add_prefix(prefix)添加前缀
DataFrame.add_suffix(suffix)添加后缀
DataFrame.align(other[, join, axis, level, …])Align two object on their axes with the
DataFrame.drop(labels[, axis, level, …])返回删除的列
DataFrame.drop_duplicates([subset, keep, …])Return DataFrame with duplicate rows removed, optionally only
DataFrame.duplicated([subset, keep])Return boolean Series denoting duplicate rows, optionally only
DataFrame.equals(other)两个数据框是否相同
DataFrame.filter([items, like, regex, axis])过滤特定的子数据框
DataFrame.first(offset)Convenience method for subsetting initial periods of time series data based on a date offset.
DataFrame.head([n])返回前n行
DataFrame.idxmax([axis, skipna])Return index of first occurrence of maximum over requested axis.
DataFrame.idxmin([axis, skipna])Return index of first occurrence of minimum over requested axis.
DataFrame.last(offset)Convenience method for subsetting final periods of time series data based on a date offset.
DataFrame.reindex([index, columns])Conform DataFrame to new index with optional filling logic, placing NA/NaN in locations having no value in the previous index.
DataFrame.reindex_axis(labels[, axis, …])Conform input object to new index with optional filling logic, placing NA/NaN in locations having no value in the previous index.
DataFrame.reindex_like(other[, method, …])Return an object with matching indices to myself.
DataFrame.rename([index, columns])Alter axes input function or functions.
DataFrame.rename_axis(mapper[, axis, copy, …])Alter index and / or columns using input function or functions.
DataFrame.reset_index([level, drop, …])For DataFrame with multi-level index, return new DataFrame with labeling information in the columns under the index names, defaulting to ‘level_0’, ‘level_1’, etc.
DataFrame.sample([n, frac, replace, …])返回随机抽样
DataFrame.select(crit[, axis])Return data corresponding to axis labels matching criteria
DataFrame.set_index(keys[, drop, append, …])Set the DataFrame index (row labels) using one or more existing columns.
DataFrame.tail([n])返回最后几行
DataFrame.take(indices[, axis, convert, is_copy])Analogous to ndarray.take
DataFrame.truncate([before, after, axis, copy])Truncates a sorted NDFrame before and/or after some particular index value.

处理缺失值

方法描述
DataFrame.dropna([axis, how, thresh, …])Return object with labels on given axis omitted where alternately any
DataFrame.fillna([value, method, axis, …])填充空值
DataFrame.replace([to_replace, value, …])Replace values given in ‘to_replace’ with ‘value’.

从新定型&排序&转变形态

方法描述
DataFrame.pivot([index, columns, values])Reshape data (produce a “pivot” table) based on column values.
DataFrame.reorder_levels(order[, axis])Rearrange index levels using input order.
DataFrame.sort_values(by[, axis, ascending, …])Sort by the values along either axis
DataFrame.sort_index([axis, level, …])Sort object by labels (along an axis)
DataFrame.nlargest(n, columns[, keep])Get the rows of a DataFrame sorted by the n largest values of columns.
DataFrame.nsmallest(n, columns[, keep])Get the rows of a DataFrame sorted by the n smallest values of columns.
DataFrame.swaplevel([i, j, axis])Swap levels i and j in a MultiIndex on a particular axis
DataFrame.stack([level, dropna])Pivot a level of the (possibly hierarchical) column labels, returning a DataFrame (or Series in the case of an object with a single level of column labels) having a hierarchical index with a new inner-most level of row labels.
DataFrame.unstack([level, fill_value])Pivot a level of the (necessarily hierarchical) index labels, returning a DataFrame having a new level of column labels whose inner-most level consists of the pivoted index labels.
DataFrame.melt([id_vars, value_vars, …])“Unpivots” a DataFrame from wide format to long format, optionally
DataFrame.TTranspose index and columns
DataFrame.to_panel()Transform long (stacked) format (DataFrame) into wide (3D, Panel) format.
DataFrame.to_xarray()Return an xarray object from the pandas object.
DataFrame.transpose(*args, **kwargs)Transpose index and columns

Combining& joining&merging

方法描述
DataFrame.append(other[, ignore_index, …])追加数据
DataFrame.assign(**kwargs)Assign new columns to a DataFrame, returning a new object (a copy) with all the original columns in addition to the new ones.
DataFrame.join(other[, on, how, lsuffix, …])Join columns with other DataFrame either on index or on a key column.
DataFrame.merge(right[, how, on, left_on, …])Merge DataFrame objects by performing a database-style join operation by columns or indexes.
DataFrame.update(other[, join, overwrite, …])Modify DataFrame in place using non-NA values from passed DataFrame.

时间序列

方法描述
DataFrame.asfreq(freq[, method, how, …])将时间序列转换为特定的频次
DataFrame.asof(where[, subset])The last row without any NaN is taken (or the last row without
DataFrame.shift([periods, freq, axis])Shift index by desired number of periods with an optional time freq
DataFrame.first_valid_index()Return label for first non-NA/null value
DataFrame.last_valid_index()Return label for last non-NA/null value
DataFrame.resample(rule[, how, axis, …])Convenience method for frequency conversion and resampling of time series.
DataFrame.to_period([freq, axis, copy])Convert DataFrame from DatetimeIndex to PeriodIndex with desired
DataFrame.to_timestamp([freq, how, axis, copy])Cast to DatetimeIndex of timestamps, at beginning of period
DataFrame.tz_convert(tz[, axis, level, copy])Convert tz-aware axis to target time zone.
DataFrame.tz_localize(tz[, axis, level, …])Localize tz-naive TimeSeries to target time zone.

作图

方法描述
DataFrame.plot([x, y, kind, ax, ….])DataFrame plotting accessor and method
DataFrame.plot.area([x, y])面积图Area plot
DataFrame.plot.bar([x, y])垂直条形图Vertical bar plot
DataFrame.plot.barh([x, y])水平条形图Horizontal bar plot
DataFrame.plot.box([by])箱图Boxplot
DataFrame.plot.density(**kwds)核密度Kernel Density Estimate plot
DataFrame.plot.hexbin(x, y[, C, …])Hexbin plot
DataFrame.plot.hist([by, bins])直方图Histogram
DataFrame.plot.kde(**kwds)核密度Kernel Density Estimate plot
DataFrame.plot.line([x, y])线图Line plot
DataFrame.plot.pie([y])饼图Pie chart
DataFrame.plot.scatter(x, y[, s, c])散点图Scatter plot
DataFrame.boxplot([column, by, ax, …])Make a box plot from DataFrame column optionally grouped by some columns or
DataFrame.hist(data[, column, by, grid, …])Draw histogram of the DataFrame’s series using matplotlib / pylab.

转换为其他格式

方法描述
DataFrame.from_csv(path[, header, sep, …])Read CSV file (DEPRECATED, please use pandas.read_csv() instead).
DataFrame.from_dict(data[, orient, dtype])Construct DataFrame from dict of array-like or dicts
DataFrame.from_items(items[, columns, orient])Convert (key, value) pairs to DataFrame.
DataFrame.from_records(data[, index, …])Convert structured or record ndarray to DataFrame
DataFrame.info([verbose, buf, max_cols, …])Concise summary of a DataFrame.
DataFrame.to_pickle(path[, compression, …])Pickle (serialize) object to input file path.
DataFrame.to_csv([path_or_buf, sep, na_rep, …])Write DataFrame to a comma-separated values (csv) file
DataFrame.to_hdf(path_or_buf, key, **kwargs)Write the contained data to an HDF5 file using HDFStore.
DataFrame.to_sql(name, con[, flavor, …])Write records stored in a DataFrame to a SQL database.
DataFrame.to_dict([orient, into])Convert DataFrame to dictionary.
DataFrame.to_excel(excel_writer[, …])Write DataFrame to an excel sheet
DataFrame.to_json([path_or_buf, orient, …])Convert the object to a JSON string.
DataFrame.to_html([buf, columns, col_space, …])Render a DataFrame as an HTML table.
DataFrame.to_feather(fname)write out the binary feather-format for DataFrames
DataFrame.to_latex([buf, columns, …])Render an object to a tabular environment table.
DataFrame.to_stata(fname[, convert_dates, …])A class for writing Stata binary dta files from array-like objects
DataFrame.to_msgpack([path_or_buf, encoding])msgpack (serialize) object to input file path
DataFrame.to_gbq(destination_table, project_id)Write a DataFrame to a Google BigQuery table.
DataFrame.to_records([index, convert_datetime64])Convert DataFrame to record array.
DataFrame.to_sparse([fill_value, kind])Convert to SparseDataFrame
DataFrame.to_dense()Return dense representation of NDFrame (as opposed to sparse)
DataFrame.to_string([buf, columns, …])Render a DataFrame to a console-friendly tabular output.
DataFrame.to_clipboard([excel, sep])Attempt to write text representation of object to the system clipboard This can be pasted into Excel, for example.

参考文献:

http://pandas.pydata.org/pandas-docs/stable/api.html#dataframe

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