python - 为 pandas 数据框中的单元格赋值

Question

我正在迭代文件，并希望根据索引和列设置 DataFrame 中的单元格值。

f = "D:/Technical_Data/1pep.csv"
df = pd.read_csv(f, header=0, sep=',')
save_file = "D:/Result_of_TA/" + "def.csv"
qbfile = open(save_file,"r")
for aline in qbfile.readlines():
    values = aline.split(",")
    if values[58].strip()=='BUY' :
       no_of_shares = price/float(values[4])
    if values[58].strip()=='SELL' :
        price = no_of_shares * float(values[4]) 
    df.ix[values[0],'Price'] = price
qbfile.close()
df.to_csv(save_file)

我遇到以下错误

  File "pandas\index.pyx", line 137, in pandas.index.IndexEngine.get_loc (pandas\index.c:3979)
  File "pandas\index.pyx", line 152, in pandas.index.IndexEngine.get_loc (pandas\index.c:3782)
  File "pandas\index.pyx", line 178, in pandas.index.IndexEngine._get_loc_duplicates (pandas\index.c:4213)
  File "pandas\index.pyx", line 385, in pandas.index.Int64Engine._maybe_get_bool_indexer (pandas\index.c:7683)
KeyError: '20150101'

两个文件中的第 0 列都是索引

Answer 1

我建议使用 pandas 读取两个 csv 文件，而不是循环通过 save_file。然后，您可以创建各种索引方案和计算，将数据从 qb 移动到 1pep。您可以构建您的代码类似这样的

import pandas as pd

# File locations
pep1_file = 'D:/Technical_Data/1pep.csv'
qb_file = 'D:/Result_of_TA/def.csv.csv'

# Read csv files
pep1 = pd.read_csv(pep1_file, header=0, sep=',')
qb = pd.read_csv(qb_file, header=0, sep=',')

# Process data    
# Find rows with buy in 58th col?
buy_index = qb.iloc[:, 58].str.contains('BUY')

# Find rows with sell in 58th col?
sell_index = qb.iloc[:, 58].str.contains('SELL')

# Get something from 4th col in buy rows?
something_from_purchase = qb.ix[buy_index, 4].astype(float)

# Derive number of shares 
# Where do you get your initial price from?
# It is used before it is assigned if buy row happens first in the original code?
no_of_shares = price / something_from_purchase

# Get something from 4th col in sell rows?
something_from_sale = qb.ix[sell_index, 4].astype(float)

# Derive price
# Where do you get your initial no_of_shares from?
# It is used before it is assigned if sell row happens first in the original code?
price = no_of_shares * something_from_sale

# Assign pep1 price based on qb index
pep1.loc[qb.index, 'Price'] = price

# Then write csv file
# Are sure you want to overwrite?
pep1.to_csv(qb_file)

现在你的代码还不清楚。有一些初始值依赖性(no_of_shares 和 price)似乎是循环的，并且某些计算似乎可能是倒退的。如果没有一些示例数据或结构解释，则无法建议具体代码。