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

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.

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