我有以下DataFrame(df):
import numpy as np
import pandas as pd
df = pd.DataFrame(np.random.rand(10, 5))
我通过分配添加更多列:
df['mean'] = df.mean(1)
如何将列的意思移到前面,即将其设置为第一列,而其他列的顺序保持不变?
我有以下DataFrame(df):
import numpy as np
import pandas as pd
df = pd.DataFrame(np.random.rand(10, 5))
我通过分配添加更多列:
df['mean'] = df.mean(1)
如何将列的意思移到前面,即将其设置为第一列,而其他列的顺序保持不变?
当前回答
另一种选择是使用set_index()方法,后跟reset_index()。请注意,我们首先pop()将要移动到数据帧前面的列,以便在重置索引时避免名称冲突:
df.set_index(df.pop('column_name'), inplace=True)
df.reset_index(inplace=True)
有关详细信息,请参阅How to change the order of dataframe columns in panda。
其他回答
你也可以这样做:
df = df[['mean', '0', '1', '2', '3']]
您可以通过以下方式获取列列表:
cols = list(df.columns.values)
输出将产生:
['0', '1', '2', '3', 'mean']
…然后,在将其放入第一个函数之前,可以手动重新排列
我认为这个函数更简单。您只需在开始或结束处或同时指定列的子集:
def reorder_df_columns(df, start=None, end=None):
"""
This function reorder columns of a DataFrame.
It takes columns given in the list `start` and move them to the left.
Its also takes columns in `end` and move them to the right.
"""
if start is None:
start = []
if end is None:
end = []
assert isinstance(start, list) and isinstance(end, list)
cols = list(df.columns)
for c in start:
if c not in cols:
start.remove(c)
for c in end:
if c not in cols or c in start:
end.remove(c)
for c in start + end:
cols.remove(c)
cols = start + cols + end
return df[cols]
我尝试了创建一个order函数,您可以使用Stata的order命令对列进行重新排序/移动。最好创建一个py文件(其名称可能是order.py),并将其保存在目录中并调用它的函数
def order(dataframe,cols,f_or_l=None,before=None, after=None):
#만든이: 김완석, Stata로 뚝딱뚝딱 저자, blog.naver.com/sanzo213 운영
# 갖다 쓰시거나 수정을 하셔도 되지만 출처는 꼭 밝혀주세요
# cols옵션 및 befor/after옵션에 튜플이 가능하게끔 수정했으며, 오류문구 수정함(2021.07.12,1)
# 칼럼이 멀티인덱스인 상태에서 reset_index()메소드 사용했을 시 적용안되는 걸 수정함(2021.07.12,2)
import pandas as pd
if (type(cols)==str) or (type(cols)==int) or (type(cols)==float) or (type(cols)==bool) or type(cols)==tuple:
cols=[cols]
dd=list(dataframe.columns)
for i in cols:
i
dd.remove(i) #cols요소를 제거함
if (f_or_l==None) & ((before==None) & (after==None)):
print('f_or_l옵션을 쓰시거나 아니면 before옵션/after옵션 쓰셔야되요')
if ((f_or_l=='first') or (f_or_l=='last')) & ~((before==None) & (after==None)):
print('f_or_l옵션 사용시 before after 옵션 사용불가입니다.')
if (f_or_l=='first') & (before==None) & (after==None):
new_order=cols+dd
dataframe=dataframe[new_order]
return dataframe
if (f_or_l=='last') & (before==None) & (after==None):
new_order=dd+cols
dataframe=dataframe[new_order]
return dataframe
if (before!=None) & (after!=None):
print('before옵션 after옵션 둘다 쓸 수 없습니다.')
if (before!=None) & (after==None) & (f_or_l==None):
if not((type(before)==str) or (type(before)==int) or (type(before)==float) or
(type(before)==bool) or ((type(before)!=list)) or
((type(before)==tuple))):
print('before옵션은 칼럼 하나만 입력가능하며 리스트 형태로도 입력하지 마세요.')
else:
b=dd[:dd.index(before)]
a=dd[dd.index(before):]
new_order=b+cols+a
dataframe=dataframe[new_order]
return dataframe
if (after!=None) & (before==None) & (f_or_l==None):
if not((type(after)==str) or (type(after)==int) or (type(after)==float) or
(type(after)==bool) or ((type(after)!=list)) or
((type(after)==tuple))):
print('after옵션은 칼럼 하나만 입력가능하며 리스트 형태로도 입력하지 마세요.')
else:
b=dd[:dd.index(after)+1]
a=dd[dd.index(after)+1:]
new_order=b+cols+a
dataframe=dataframe[new_order]
return dataframe
下面的python代码是我制作的order函数的一个示例。我希望您可以使用我的order函数轻松地对列进行重新排序:)
# module
import pandas as pd
import numpy as np
from order import order # call order function from order.py file
# make a dataset
columns='a b c d e f g h i j k'.split()
dic={}
n=-1
for i in columns:
n+=1
dic[i]=list(range(1+n,10+1+n))
data=pd.DataFrame(dic)
print(data)
# use order function (1) : order column e in the first
data2=order(data,'e',f_or_l='first')
print(data2)
# use order function (2): order column e in the last , "data" dataframe
print(order(data,'e',f_or_l='last'))
# use order function (3) : order column i before column c in "data" dataframe
print(order(data,'i',before='c'))
# use order function (4) : order column g after column b in "data" dataframe
print(order(data,'g',after='b'))
# use order function (4) : order columns ['c', 'd', 'e'] after column i in "data" dataframe
print(order(data,['c', 'd', 'e'],after='i'))
DataFrame.sort_index(axis=1)非常干净。请在此处检查文档。然后凹入
要根据其他列的名称将现有列设置为右侧/左侧,请执行以下操作:
def df_move_column(df, col_to_move, col_left_of_destiny="", right_of_col_bool=True):
cols = list(df.columns.values)
index_max = len(cols) - 1
if not right_of_col_bool:
# set left of a column "c", is like putting right of column previous to "c"
# ... except if left of 1st column, then recursive call to set rest right to it
aux = cols.index(col_left_of_destiny)
if not aux:
for g in [x for x in cols[::-1] if x != col_to_move]:
df = df_move_column(
df,
col_to_move=g,
col_left_of_destiny=col_to_move
)
return df
col_left_of_destiny = cols[aux - 1]
index_old = cols.index(col_to_move)
index_new = 0
if len(col_left_of_destiny):
index_new = cols.index(col_left_of_destiny) + 1
if index_old == index_new:
return df
if index_new < index_old:
index_new = np.min([index_new, index_max])
cols = (
cols[:index_new]
+ [cols[index_old]]
+ cols[index_new:index_old]
+ cols[index_old + 1 :]
)
else:
cols = (
cols[:index_old]
+ cols[index_old + 1 : index_new]
+ [cols[index_old]]
+ cols[index_new:]
)
df = df[cols]
return df
E.g.
cols = list("ABCD")
df2 = pd.DataFrame(np.arange(4)[np.newaxis, :], columns=cols)
for k in cols:
print(30 * "-")
for g in [x for x in cols if x != k]:
df_new = df_move_column(df2, k, g)
print(f"{k} after {g}: {df_new.columns.values}")
for k in cols:
print(30 * "-")
for g in [x for x in cols if x != k]:
df_new = df_move_column(df2, k, g, right_of_col_bool=False)
print(f"{k} before {g}: {df_new.columns.values}")
输出: