我有一个循环,该循环采用一系列现有的数据帧并操纵其格式和值。我需要知道如何在循环结束时创建包含已修改内容的新数据框。
示例如下:
import pandas as pd
# Create datasets
First = {'GDP':[200,175,150,100]}
Second = {'GDP':[550,200,235,50]}
# Create old_dataframes
old_df_1 = pd.DataFrame(First)
old_df_2 = pd.DataFrame(Second)
# Define references and dictionary
old_dfs = [old_df_1, old_df_2]
new_dfs = ['new_df_1','new_df_2']
dictionary = {}
# Begin Loop
for df, name in zip(old_dfs, new_dfs):
# Multiply all GDP values by 1.5 in both dataframes
df = df * 1.5
# ISSUE HERE - Supposed to Create new data frames 'new_df_1' & 'new_df_2' containing df*1.5 values: Only appends to dictionary. Does not create new_df_1 & new_df_2
dictionary[name] = df
# Check for the existance of 'new_df_1 & new_df_2' (They will not appear)
%who_ls DataFrame
问题:我已经在上面标记了问题。我的代码未创建“ new_df_1”和“ new_df_2”数据框。它只是将它们附加到字典中。我需要能够将new_df_1和new_df_2 创建为单独的数据框。
答案 0 :(得分:0)
from copy import deepcopy # to copy old dataframes appropriately
# create 2 lists, first holds old dataframes and second holds modified ones
old_dfs_list, new_dfs_list = [pd.DataFrame(First), pd.DataFrame(Second)], []
# process old dfs one by one by iterating over old_dfs_list,
# copy, modify each and append it to list of new_dfs_list with same index as
# old df ... so old_dfs_list[1] is mapped to new_dfs_list[1]
for i in range(len(old_dfs_list)):
# a deep copy prevent changing old dfs by reference
df_deep_copy = deepcopy(old_dfs_list[i])
df_deep_copy['GDP'] *= 1.5
new_dfs_list.append(df_deep_copy)
print( old_dfs_list[0] ) # to check that old dfs are not changed
print( new_dfs_list[0] )
您也可以尝试使用字典而不是列表来使用您喜欢的名称:
import pandas as pd
datadicts_dict = {
'first' :{'GDP':[200,175,150,100]},
'second':{'GDP':[550,200,235,50]},
'third' :{'GDP':[600,400,520,100, 800]}
}
# Create datasets and store it in a python dictionary
old_dfs_dict, new_dfs_dict = {}, {} # initialize 2 dicts to hold original and modified dataframes
# process datasets one by one by iterating over datadicts_dict,
# convert to df save it in old_dfs_dict with same name as the key
# copy, modify each and put it in new_dfs_dict with same key
# so dataset of key 'first' in datadicts_dict is saved as old_dfs_dict['first']
# modified and mapped to new_dfs_dict['first']
for dataset_name, data_dict in datadicts_dict.items():
old_dfs_dict[dataset_name] = pd.DataFrame({'GDP':data_dict['GDP']})
new_dfs_dict[dataset_name] = pd.DataFrame({'GDP':data_dict['GDP']}) * 1.5
print( old_dfs_dict['third'] ) # to check that old dfs are not changed
print( new_dfs_dict['third'] )
答案 1 :(得分:0)
最后,我通过思考以上答案,终于找到了可行的解决方案。我面临的问题是-从字典内部提取附加数据。我真的没有想到我可以从循环的外部字典中提取数据,然后形成数据框。
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# Begin Loop
for df, name in zip(old_dfs, new_dfs):
# Multiply all GDP values by 1.5 in both dataframes
df = df * 1.5
# ISSUE HERE - Supposed to Create new data frames 'new_df_1' & 'new_df_2' containing df*1.5 values: Only appends to dictionary. Does not create new_df_1 & new_df_2
dictionary[name] = df
# Solution - Extract from Dictionary and form Dataframe
new_df_1 = pd.DataFrame.from_dict(dictionary['new_df_1'])
new_df_2 = pd.DataFrame.from_dict(dictionary['new_df_2'])
# Check for the existance of 'new_df_1 & new_df_2'
%who_ls DataFrame