在python中有没有办法把一列转换成多列？

Question

我有一个数据，它只在一列中具有以下结构：

Datetime stamp 1
Obs1
Obs2
Obs3
Datetime stamp 2
Obs1
Obs2
Obs3

我想像上面那样转换它。使得日期时间将是标题，且该特定日期时间所有of将成为该特定日期时间戳的行

Date time stamp 1.     Date time stamp2
Obs1                         Obs1
Obs2.                         obs2
Obs3.                         Obs3

Answer 1

假设您的单列存储在列表/数组中，您可以像这样制作所需的子列表：

lst = ['Datetime stamp 1', 'Obs1', 'Obs2', 'Obs3', 'Datetime stamp 2', 'Obs1', 'Obs2', 'Obs3']

result = []
temp = [lst[0]]
for item in lst[1:]:
    if item.startswith('Datetime'):
        result.append(temp)
        temp = [item]
    else:
        temp.append(item)

result.append(temp)
print(result)

输出：

[['Datetime stamp 1', 'Obs1', 'Obs2', 'Obs3'], ['Datetime stamp 2', 'Obs1', 'Obs2', 'Obs3']]

它现在是一个列表列表，其中的每个元素都可以为您表示一列。

Answer 2

假设格式始终相同(即所有拆分都以字符串“Datetime”开头)，您可以获得字符串以"Datetime"开头的索引，并选择每个拆分之间的所有数据：

import pandas as pd

data = pd.Series(["Datetime stamp 1",
"Obs1",
"Obs2",
"Obs3",
"Datetime stamp 2",
"Obs1",
"Obs2",
"Obs3"])


#Get splits
idx_split =data.str.startswith("Datetime ")
idx_split = idx_split.index[idx_split] # [0,4]


N_COLS = len(idx_split) #number of columns
vals = [0]*N_COLS #Initialize values

#Loop over each split-index and slize data
for i in range(N_COLS-1):
    vals[i] = list(data[idx_split[i]:idx_split[i+1]])
vals[i+1] = list(data[idx_split[-1]:]) #Get the last one

print(vals)
#[['Datetime stamp 1', 'Obs1', 'Obs2', 'Obs3'],
#['Datetime stamp 2', 'Obs1', 'Obs2', 'Obs3']]


#Get the first element from each list and use that as column name
# + remove it
cols = [p.pop(0) for p in vals] 


#The data list is in wrong shape for pandas, use https://stackoverflow.com/questions/6473679/transpose-list-of-lists to transpose the list to right shape

df = pd.DataFrame(list(map(list, zip(*vals))),columns = cols)
print(df)

#Datetime stamp 1   Datetime stamp 2
#0  Obs1    Obs1
#1  Obs2    Obs2
#2  Obs3    Obs3