# str **Series.str**是处理字符串列的方法, 拥有的方法与python中原有的字符串`str`对象的方法非常类似, 只是个别的方法不同, 下面记录一些常用的重要方法. ## Series.str.cat ```python Series.str.cat(others=None, sep=None, na_rep=None, join=None) ``` 作用是将两个Series对应位置进行合并, 要求两者的长度相同. * others: Series, Index, DataFrame, np.ndarrary or list-like * 给出的类列表对象长度应该与调用者的长度相同, 然后将两个列表对应索引位置的字符串合并, 组成新的Series * 如果没有给出`others`, 则将调用者的所有字符串合并在一起, 返回一个字符串 ```python >>> s = pd.Series(['a', 'b', np.nan, 'd']) >>> s.str.cat(sep=' ') 'a b d' ``` * sep: str, default ‘’ * 分隔符 * na\_rep: str or None, default None * 用来代替`missing values`的字符 * 如果是`None`, 将`missing value`从最终结果中移除 * join: {‘left’, ‘right’, ‘outer’, ‘inner’}, default None * 需要调用者与传入的对象都是拥有`index`的`Series`, 然后根据`index`进行`merge`操作 例子: ```python >>> s = pd.Series(['a', 'b', np.nan, 'd']) >>> s.str.cat(sep=' ') 'a b d' >>> s.str.cat(sep=' ', na_rep='?') 'a b ? d' ``` ```python >>> s.str.cat(['A', 'B', 'C', 'D'], sep=',') 0 a,A 1 b,B 2 NaN 3 d,D dtype: object >>> s.str.cat(['A', 'B', 'C', 'D'], sep=',', na_rep='-') 0 a,A 1 b,B 2 -,C 3 d,D dtype: object >>> s.str.cat(['A', 'B', 'C', 'D'], na_rep='-') 0 aA 1 bB 2 -C 3 dD dtype: object ``` ```python >>> t = pd.Series(['d', 'a', 'e', 'c'], index=[3, 0, 4, 2]) >>> s.str.cat(t, join='left', na_rep='-') 0 aa 1 b- 2 -c 3 dd dtype: object >>> >>> s.str.cat(t, join='outer', na_rep='-') 0 aa 1 b- 2 -c 3 dd 4 -e dtype: object >>> >>> s.str.cat(t, join='inner', na_rep='-') 0 aa 2 -c 3 dd dtype: object >>> >>> s.str.cat(t, join='right', na_rep='-') 3 dd 0 aa 4 -e 2 -c dtype: object ``` ## Series.str.split / Series.str.rsplit ```python Series.str.split(pat=None, n=-1, expand=False) Series.str.rsplit(pat=None, n=-1, expand=False) ``` 对Series中的每个字符串按指定的分割符进行分割, 注意可以直接扩展成**DataFrame**. **split**/**rsplit**一个是从左向右, 一个从右向左分割. * pat: str, optional * 分割符, 如果不指定, 则默认为`whitespace` * n: int, default -1 (all) * 限定每个元素划分的次数, 即最多返回`n+1`个元素, 如果指定为`0`, `-1`或者`None`则返回所有结果 * 满足最大分割次数之后, 剩余的结果将不再分割, 直接作为最后的结果返回 * expand: bool, default False * 是否将分割的结果扩展到多个列中, 组成DataFrame * **True**: 返回扩展后的**DataFrame**/MultiIndex * **False**: 返回的仍是**Series**/Index ```python >>> s = pd.Series(["this is a regular sentence", "https://docs.python.org/3/tutorial/index.html", np.nan]) >>> s.str.split() 0 [this, is, a, regular, sentence] 1 [https://docs.python.org/3/tutorial/index.html] 2 NaN dtype: object ``` ```python >>> s.str.split(n=2) 0 [this, is, a regular sentence] 1 [https://docs.python.org/3/tutorial/index.html] 2 NaN dtype: object >>> s.str.rsplit(n=2) 0 [this is a, regular, sentence] 1 [https://docs.python.org/3/tutorial/index.html] 2 NaN dtype: object ``` ```python >>> s.str.split(pat = "/") 0 [this is a regular sentence] 1 [https:, , docs.python.org, 3, tutorial, index... 2 NaN dtype: object ``` ```python >>> s.str.split(expand=True) 0 1 2 3 0 this is a regular 1 https://docs.python.org/3/tutorial/index.html None None None 2 NaN NaN NaN NaN 4 0 sentence 1 None 2 NaN >>> s.str.rsplit("/", n=1, expand=True) 0 1 0 this is a regular sentence None 1 https://docs.python.org/3/tutorial index.html 2 NaN NaN ``` ## Series.str.join ```python Series.str.join(sep) ``` 与**Series.str.split / Series.str.rsplit**的作用相反, 接受每个元素为一个列表, 将列表与连接符组合在一起形成一个字符串. * sep: 分隔符 **注意**: 如果列表中任何一个元素为**非字符串**, 最后返回的结果为**NaN**. 详情见下面的例子. ```python >>> s = pd.Series([['lion', 'elephant', 'zebra'], ... [1.1, 2.2, 3.3], ... ['cat', np.nan, 'dog'], ... ['cow', 4.5, 'goat'], ... ['duck', ['swan', 'fish'], 'guppy']]) >>> s 0 [lion, elephant, zebra] 1 [1.1, 2.2, 3.3] 2 [cat, nan, dog] 3 [cow, 4.5, goat] 4 [duck, [swan, fish], guppy] dtype: object >>> s.str.join('-') 0 lion-elephant-zebra 1 NaN 2 NaN 3 NaN 4 NaN dtype: object ``` ## [Series.str.get\_dummies](http://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.Series.str.get_dummies.html#pandas.Series.str.get_dummies) ```python Series.str.get_dummies(sep='|') ``` 与上面的`split`方法类似, 但此时的输入的每个元素虽然是有分隔符的字符串, 但所有元素分隔出来的结果集合是有限的, 用来做`One-Hot`. * sep: string, default “|” * 分隔符 ```python >>> pd.Series(['a|b', 'a', 'a|c']).str.get_dummies() a b c 0 1 1 0 1 1 0 0 2 1 0 1 >>> pd.Series(['a|b', np.nan, 'a|c']).str.get_dummies() a b c 0 1 1 0 1 0 0 0 2 1 0 1 ``` ## [Series.str.contains](http://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.Series.str.contains.html#pandas.Series.str.contains) ```python Series.str.contains(pat, case=True, flags=0, na=nan, regex=True) ``` 判断是否包含指定的内容, 传入的可以是一个字符串, 也可以使用**正则表达式** * pat: str * 字符串或正则表达式 * case: bool, default True * 是否关心大小写 * regex: bool, default True * 是否使用正则表达式 * flags: int, default 0 (no flags) * 正则表达式的模式, **re**模块使用, 例如`re.IGNORECASE` * na: default NaN * 填补缺失位置的值 ```python >>> ind = pd.Index(['Mouse', 'dog', 'house and parrot', '23.0', np.NaN]) >>> ind.str.contains('23', regex=False) Index([False, False, False, True, nan], dtype='object') >>> s1.str.contains('oG', case=True, regex=True) 0 False 1 False 2 False 3 False 4 NaN dtype: object >>> s1.str.contains('house|dog', regex=True) 0 False 1 True 2 True 3 False 4 NaN dtype: object ``` ```python >>> s2 = pd.Series(['40','40.0','41','41.0','35']) >>> s2.str.contains('.0', regex=True) 0 True 1 True 2 False 3 True 4 False dtype: bool ``` --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. 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