Question

我有一个for-while循环组合来检查人年观测值的差异。整个过程为我提供了一个布尔列表，作为结果，我需要对其进行进一步分析。

我尝试了append的多个版本，但没有一个起作用。

这是我的数据：

import pandas as pd
df = pd.DataFrame({'year': ['2001', '2004', '2005', '2006', '2007', '2008', '2009',
                             '2003', '2004', '2005', '2006', '2007', '2008', '2009',
                            '2003', '2004', '2005', '2006', '2007', '2008', '2009'],
                   'id': ['1', '1', '1', '1', '1', '1', '1', 
                          '2', '2', '2', '2', '2', '2', '2',
                         '5', '5', '5','5', '5', '5', '5'],
                   'money': ['15', '15', '15', '21', '21', '21', '21', 
                             '17', '17', '17', '20', '17', '17', '17',
                            '25', '30', '22', '25', '8', '7', '12']}).astype(int)

这是我的代码：

# for every person
for i in df.id.unique():
    # find the first and last index value
    first = df[df['id']==i].index.values.astype(int)[0] 
    last = df[df['id']==i].index.values.astype(int)[-1] 
    # first element has to be kept
    print(False)
    # for all elements, compare values next to each other
    while first < last:
        abs_diff = abs( df['money'][first] - df['money'][first+1] ) > 0
        # print TRUE, when adjacent values differ
        print(abs_diff)
        # update the counter
        first +=1

它返回一个布尔列表，即： FalseFalseFalseTrueFalseFalseFalseFalseFalseFalseFalseTrueTrueFalseFalseFalseTrueTrueTrueTrueTrueTrueTrue

问题：如何将循环输出保存在列表中？

Answer 1

IIUC使用groupby，diff，fillna和ne：

df.groupby('id')['money'].diff().fillna(0).ne(0).to_list()

[出]

[False,
 False,
 False,
 True,
 False,
 False,
 False,
 False,
 False,
 False,
 True,
 True,
 False,
 False,
 False,
 True,
 True,
 True,
 True,
 True,
 True]

Answer 2

尝试

import pandas as pd
df = pd.DataFrame({'year': ['2001', '2004', '2005', '2006', '2007', '2008', '2009',
                             '2003', '2004', '2005', '2006', '2007', '2008', '2009',
                            '2003', '2004', '2005', '2006', '2007', '2008', '2009'],
                   'id': ['1', '1', '1', '1', '1', '1', '1',
                          '2', '2', '2', '2', '2', '2', '2',
                         '5', '5', '5','5', '5', '5', '5'],
                   'money': ['15', '15', '15', '21', '21', '21', '21',
                             '17', '17', '17', '20', '17', '17', '17',
                            '25', '30', '22', '25', '8', '7', '12']}).astype(int)
# for every person
l=list()
for i in df.id.unique():
    # find the first and last index value
    first = df[df['id']==i].index.values.astype(int)[0]
    last = df[df['id']==i].index.values.astype(int)[-1]
    # first element has to be kept
    print(False)
    l.append(False)
    # my try: diff = []

    # for all elements, compare values next to each other
    while first < last:
        abs_diff = abs( df['money'][first] - df['money'][first+1] ) > 0
        # print TRUE, when adjacent values differ
        l.append(abs_diff)
        # my try: diff.append(abs_diff)

        # update the counter
        first +=1
print(l)

输出：

[False, False, False, True, False, False, False, False, False, False, True, True, False, False, False, True, True, True, True, True, True]

Answer 3

如果我正确理解了您的问题，则只需在for循环之外定义变量：

output = list()

for i in df.id.unique():
    # find the first and last index value
    first = df[df['id']==i].index.values.astype(int)[0] 
    last = df[df['id']==i].index.values.astype(int)[-1] 
    # first element has to be kept
    output.append(False)

    # for all elements, compare values next to each other
    while first < last:
        abs_diff = abs( df['money'][first] - df['money'][first+1] ) > 0
        # print TRUE, when adjacent values differ
        output.append(abs_diff)

        # update the counter
        first +=1
print(output)

此刻，您每次都需要重新设置值，这样最终只能得到最后一个id的输出。

Answer 4

from collections import defaultdict
result = defaultdict(list)
for i in df.id.unique():
    # find the first and last index value
    first = df[df['id']==i].index.values.astype(int)[0] 
    last = df[df['id']==i].index.values.astype(int)[-1] 
    # first element has to be kept
    print(False)
    result.append("False")

    # my try: diff = [] 

    # for all elements, compare values next to each other
    while first < last:
        abs_diff = abs( df['money'][first] - df['money'][first+1] ) > 0
        # print TRUE, when adjacent values differ
        print(abs_diff)
        result[i].append(abs_diff)

        # my try: diff.append(abs_diff)

        # update the counter
        first +=1

我想如果您想为每个人分别保存ID会起作用。

如何在Python的for循环中保存while循环的输出？

4 个答案: