pandas :列的长度必须与键的长度相同 [英] pandas: columns must be same length as key

问题描述

我正在尝试将几列重新设置为字符串格式(它们包含NaN，所以我不能只将它们读取为整数).当前所有列均是float64，我要使其不包含小数.

I'm trying to re-format several columns into strings (they contain NaNs, so I can't just read them in as integers). All of the columns are currently float64, and I want to make it so they don't have decimals.

以下是数据:

{'crash_id': {0: 201226857.0,
  1: 201226857.0,
  2: 2012272611.0,
  3: 2012272611.0,
  4: 2012298998.0},
 'driver_action1': {0: 1.0, 1: 1.0, 2: 29.0, 3: 1.0, 4: 3.0},
 'driver_action2': {0: 99.0, 1: 99.0, 2: 1.0, 3: 99.0, 4: 99.0},
 'driver_action3': {0: 99.0, 1: 99.0, 2: 99.0, 3: 99.0, 4: 99.0},
 'driver_action4': {0: 99.0, 1: 99.0, 2: 99.0, 3: 99.0, 4: 99.0},
 'harmful_event1': {0: 14.0, 1: 14.0, 2: 14.0, 3: 14.0, 4: 14.0},
 'harmful_event2': {0: 99.0, 1: 99.0, 2: 99.0, 3: 99.0, 4: 99.0},
 'harmful_event3': {0: 99.0, 1: 99.0, 2: 99.0, 3: 99.0, 4: 99.0},
 'harmful_event4': {0: 99.0, 1: 99.0, 2: 99.0, 3: 99.0, 4: 99.0},
 'most_damaged_area': {0: 14.0, 1: 2.0, 2: 14.0, 3: 14.0, 4: 3.0},
 'most_harmful_event': {0: 14.0, 1: 14.0, 2: 14.0, 3: 14.0, 4: 14.0},
 'point_of_impact': {0: 15.0, 1: 1.0, 2: 14.0, 3: 14.0, 4: 1.0},
 'vehicle_id': {0: 20121.0, 1: 20122.0, 2: 20123.0, 3: 20124.0, 4: 20125.0},
 'vehicle_maneuver': {0: 3.0, 1: 1.0, 2: 4.0, 3: 1.0, 4: 1.0}}

当我尝试将这些列转换为字符串时，会发生以下情况:

When I try to convert those columns to string, this is what happens:

>> df[['crash_id','vehicle_id','point_of_impact','most_damaged_area','most_harmful_event','vehicle_maneuver','harmful_event1','harmful_event2','harmful_event3','harmful_event4','driver_action1','driver_action2','driver_action3','driver_action4']] = df[['crash_id','vehicle_id','point_of_impact','most_damaged_area','most_harmful_event','vehicle_maneuver','harmful_event1','harmful_event2','harmful_event3','harmful_event4','driver_action1','driver_action2','driver_action3','driver_action4']].applymap(lambda x: '{:.0f}'.format(x))

File "C:\Users\<name>\AppData\Local\Continuum\Anaconda3\lib\site-packages\pandas\core\frame.py", line 2376, in _setitem_array
        raise ValueError('Columns must be same length as key')

ValueError: Columns must be same length as key

我以前从未见过此错误，觉得这很简单...我在做什么错了?

I've never seen this error before and feel like this is something simple...what am I doing wrong?

推荐答案

您的代码会使用您提供的字典为我运行.尝试创建一个函数来分别处理NaN案例；我认为是造成您的问题的原因.

Your code runs for me with the dictionary you provided. Try creating a function to deal with the NaN cases separately; I think they are causing your issues.

基本情况如下:

def formatter(x):
    if x == None:
        return None
    else:
        return '{:.0f}'.format(x)

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