[英]creating multiple columns in a for loop python
I'm new to Python. I'm trying to create multiple columns in a for loop but I'm having trouble with it.我是 Python 的新手。我正在尝试在 for 循环中创建多个列,但我遇到了麻烦。 I have several columns and I'm trying to create a new column that shows whether or not the elements in ohlcs is greater than elements in metrics.
我有几个列,我正在尝试创建一个新列来显示 ohlcs 中的元素是否大于 metrics 中的元素。 I can do it to create one column but I want to save time since I plan on doing the same function but for different variables.
我可以这样做来创建一个列,但我想节省时间,因为我计划对不同的变量执行相同的 function。
ohlcs = ['open', 'high', 'low', 'close']
metrics = ['vwap', '9EMA', '20EMA']
wip = []
for idx, row in master_df.iterrows():
for ohlc in ohlcs:
for metric in metrics:
row[f'{ohlc} above {metric}'] = np.where(row[ohlc] >= row[metric], 1, 0)
This didn't do anything.这没有做任何事情。 I've also done this:
我也这样做过:
ohlcs = ['open', 'high', 'low', 'close']
metrics = ['vwap', '9EMA', '20EMA']
wip = []
for idx, row in master_df.iterrows():
for ohlc in ohlcs:
for metric in metrics:
if master_df[ohlc] >= master_df[metric]:
master_df[f'{ohlc} above {metric}'] = 1
else:
master_df[f'{ohlc} above {metric}'] = 0
That gave me an error.那给了我一个错误。
ValueError: The truth value of a Series is ambiguous. ValueError:Series 的真值不明确。 Use a.empty, a.bool(), a.item(), a.any() or a.all().
使用 a.empty、a.bool()、a.item()、a.any() 或 a.all()。
I did other things but I erased those as I worked on it.我做了其他事情,但我在处理它时删除了它们。 At this point I'm out of ideas.
在这一点上我没主意了。 Please help!
请帮忙!
I got it now but I checked manually to see if the values lined up and it wasn't.我现在明白了,但我手动检查了值是否对齐,但事实并非如此。
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How do I fix it?我如何解决它?
There is no need to iterate over the rows of the dataframe. This will give you the required result:无需遍历 dataframe 的行。这将为您提供所需的结果:
for ohlc in ohlcs:
for metric in metrics:
master_df[f'{ohlc} over {metric}'] = (master_df[ohlc] >= master_df[metric]).astype(int)
The part astype(int)
is just to convert True
and False
into 1
and 0
, if you are okay with True
and False
representation, you can use just master_df[f'{ohlc} over {metric}'] = master_df[ohlc] >= master_df[metric]
. astype(int)
部分只是将True
和False
转换为1
和0
,如果你对True
和False
表示没问题,你可以只使用master_df[f'{ohlc} over {metric}'] = master_df[ohlc] >= master_df[metric]
。
EDIT: Of course, (master_df[ohlc] >= master_df[metric]).astype(int)
is equivalent to np.where(master_df[ohlc] >= master_df[metric], 1, 0)
, you can use either.编辑:当然,
(master_df[ohlc] >= master_df[metric]).astype(int)
等同于np.where(master_df[ohlc] >= master_df[metric], 1, 0)
,您可以使用其中任何一个。
Consider itertools.product
and the functional form DataFrame.ge
for all pairwise possibilities fir a flatter looping:考虑
itertools.product
和函数形式DataFrame.ge
以获得更平坦循环的所有成对可能性:
from itertools import product
...
ohlcs = ['open', 'high', 'low', 'close']
metrics = ['vwap', '9EMA', '20EMA']
pairs = product(ohlcs, metrics)
for ohlc, metric in pairs:
master_df[f"{ohlc} over {metric}"] = master_df[ohlc].ge(master_df[metric])
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