I have a function, which does some operations on each DataFrame column and extracts a shorter series from it (in the original code there is some time consuming calculations going on)
Then it adds it to a dictionary before it goes on with the next columns.
In the end it creates a dataframe from the dictionary and manipulates its index.
How can I parallelize the loop in which each column is manipulated?
This is a less complicated reproducable sample of the code.
import pandas as pd
raw_df = pd.DataFrame({"A":[ 1.1 ]*100000,
"B":[ 2.2 ]*100000,
"C":[ 3.3 ]*100000})
def preprocess_columns(raw_df, ):
df = {}
width = 137
for name in raw_df.columns:
'''
Note: the operations in this loop do not have a deep sense and are just for illustration of the function preprocess_columns. In the original code there are ~ 50 lines of list comprehensions etc.
'''
# 3. do some column operations. (actually theres more than just this operation)
seriesF = raw_df[[name]].dropna()
afterDropping_indices = seriesF.index.copy(deep=True)
list_ = list(raw_df[name])[width:]
df[name]=pd.Series(list_.copy(), index=afterDropping_indices[width:])
# create df from dict and reindex
df=pd.concat(df,axis=1)
df=df.reindex(df.index[::-1])
return df
raw_df = preprocess_columns(raw_df )
Maybe you can use this:
https://github.com/xieqihui/pandas-multiprocess
pip install pandas-multiprocess
from pandas_multiprocess import multi_process
args = {'width': 137}
result = multi_process(func=func, data=df, num_process=8, **args)
No matter what I do I don't seem to be able to add all the base volumes and quote volumes together easily! I want to end up with a total base volume and a total quote volume of all the data in the data frame. Can someone help me on how you can do this easily?
I have tried summing and saving the data in a dictionary first and then adding it but I just don't seem to be able to make this work!
import urllib
import pandas as pd
import json
def call_data(): # Call data from Poloniex
global df
datalink = 'https://poloniex.com/public?command=returnTicker'
df = urllib.request.urlopen(datalink)
df = df.read().decode('utf-8')
df = json.loads(df)
global current_eth_price
for k, v in df.items():
if 'ETH' in k:
if 'USDT_ETH' in k:
current_eth_price = round(float(v['last']),2)
print("Current ETH Price $:",current_eth_price)
def calc_volumes(): # Calculate the base & quote volumes
global volume_totals
for k, v in df.items():
if 'ETH' in k:
basevolume = float(v['baseVolume'])*current_eth_price
quotevolume = float(v['quoteVolume'])*float(v['last'])*current_eth_price
if quotevolume > 0:
percentages = (quotevolume - basevolume) / basevolume * 100
volume_totals = {'key':[k],
'basevolume':[basevolume],
'quotevolume':[quotevolume],
'percentages':[percentages]}
print("volume totals:",volume_totals)
print("#"*8)
call_data()
calc_volumes()
A few notes:
For the next 2 years don't use the keyword globals for anything.
put function documentation under the function in quotes
using the requests library will be much easier than urllib. However ...
pandas can fetch the JSON and parse it all in one step
ok it doesn't have to be as split up as this, I'm just showing you how to properly pass variables around instead of globals.
I could not find "ETH" by itself. In the data they sent they have these 3 ['BTC_ETH', 'USDT_ETH', 'USDC_ETH']. So I used "USDT_ETH" I hope the substitution is ok.
calc_volumes is seeming to do the calculation and being some sort of filter (it's picky as to what it prints). This function needs to be broken up in to it's two separate jobs. printing and calculating. (maybe there was a filter step but I leave that for homework)
.
import pandas as pd
eth_price_url = 'https://poloniex.com/public?command=returnTicker'
def get_data(url=''):
""" Call data from Poloniex and put it in a dataframe"""
data = pd.read_json(url)
return data
def get_current_eth_price(data = None):
""" grab the price out of the dataframe """
current_eth_price = data['USDT_ETH']['last'].round(2)
return current_eth_price
def calc_volumes(data=None, current_eth_price=None):
""" Calculate the base & quote volumes """
data = df[df.columns[df.columns.str.contains('ETH')]].loc[['baseVolume', 'quoteVolume', 'last']]
data = data.transpose()
data[['baseVolume','quoteVolume']]*= current_eth_price
data['quoteVolume']*=data['last']
data['percentages']=(data['quoteVolume'] - data['baseVolume']) / data['quoteVolume'] * 100
return data
df = get_data(url = eth_price_url)
the_price = get_current_eth_price(data = df)
print(f'the current eth price is: {the_price}')
volumes = calc_volumes(data=df, current_eth_price=the_price)
print(volumes)
This code seems kind of odd and inconsistent... for example, you're importing pandas and calling your variable df but you're not actually using dataframes. If you used df = pd.read_json('https://poloniex.com/public?command=returnTicker', 'index')* to get a dataframe, most of your data manipulation here would become much easier, and wouldn't require any loops either.
For example, the first function's code would become as simple as current_eth_price = df.loc['USDT_ETH','last'].
The second function's code would basically be
eth_rows = df[df.index.str.contains('ETH')]
total_base_volume = (eth_rows.baseVolume * current_eth_price).sum()
total_quote_volume = (eth_rows.quoteVolume * eth_rows['last'] * current_eth_price).sum()
(*The 'index' argument tells pandas to read the JSON dictionary indexed by rows, then columns, rather than columns, then rows.)
I have a pandas dataframe in the following format:
'customer_id','transaction_dt','product','price','units'
1,2004-01-02,thing1,25,47
1,2004-01-17,thing2,150,8
2,2004-01-29,thing2,150,25
3,2017-07-15,thing3,55,17
3,2016-05-12,thing3,55,47
4,2012-02-23,thing2,150,22
4,2009-10-10,thing1,25,12
4,2014-04-04,thing2,150,2
5,2008-07-09,thing2,150,43
I have written the following to create two new fields indicating 30 day windows:
import numpy as np
import pandas as pd
start_date_period = pd.period_range('2004-01-01', '12-31-2017', freq='30D')
end_date_period = pd.period_range('2004-01-30', '12-31-2017', freq='30D')
def find_window_start_date(x):
window_start_date_idx = np.argmax(x < start_date_period.end_time)
return start_date_period[window_start_date_idx]
df['window_start_dt'] = df['transaction_dt'].apply(find_window_start_date)
def find_window_end_date(x):
window_end_date_idx = np.argmin(x > end_date_period.start_time)
return end_date_period[window_end_date_idx]
df['window_end_dt'] = df['transaction_dt'].apply(find_window_end_date)
Unfortunately, this is far too slow doing the row-wise apply for my application. I would greatly appreciate any tips on vectorizing these functions if possible.
EDIT:
The resultant dataframe should have this layout:
'customer_id','transaction_dt','product','price','units','window_start_dt','window_end_dt'
It does not need to be resampled or windowed in the formal sense. It just needs 'window_start_dt' and 'window_end_dt' columns to be added. The current code works, it just need to be vectorized if possible.
EDIT 2: pandas.cut is built-in:
tt=[[1,'2004-01-02',0.1,25,47],
[1,'2004-01-17',0.2,150,8],
[2,'2004-01-29',0.2,150,25],
[3,'2017-07-15',0.3,55,17],
[3,'2016-05-12',0.3,55,47],
[4,'2012-02-23',0.2,150,22],
[4,'2009-10-10',0.1,25,12],
[4,'2014-04-04',0.2,150,2],
[5,'2008-07-09',0.2,150,43]]
start_date_period = pd.date_range('2004-01-01', '12-01-2017', freq='MS')
end_date_period = pd.date_range('2004-01-30', '12-31-2017', freq='M')
df = pd.DataFrame(tt,columns=['customer_id','transaction_dt','product','price','units'])
df['transaction_dt'] = pd.Series([pd.to_datetime(sub_t[1],format='%Y-%m-%d') for sub_t in tt])
the_cut = pd.cut(df['transaction_dt'],bins=start_date_period,right=True,labels=False,include_lowest=True)
df['win_start_test'] = pd.Series([start_date_period[int(x)] if not np.isnan(x) else 0 for x in the_cut])
df['win_end_test'] = pd.Series([end_date_period[int(x)] if not np.isnan(x) else 0 for x in the_cut])
print(df.head())
win_start_test and win_end_test should be equal to their counterparts computed using your function.
The ValueError was coming from not casting x to int in the relevant line. I also added a NaN check, though it wasn't needed for this toy example.
Note the change to pd.date_range and the use of the start-of-month and end-of-month flags M and MS, as well as converting the date strings into datetime.
I'm trying to calculate tracking error for a number of different benchmarks versus a fund that I'm looking at (tracking error is defined as the standard deviation of the percent difference between the fund and benchmark). The time series for the fund and all the benchmarks are all in a data frame that I'm reading from an excel on file and what I have so far is this (with the idea that arg1 represents all the benchmarks and is then applied using applymap), but it's returning a KeyError, any suggestions?
import pandas as pd
import numpy as np
data = pd.read_excel('File_Path.xlsx')
def index_analytics(arg1):
tracking_err = np.std((data['Fund'] - data[arg1]) / data[arg1])
return tracking_err
data.applymap(index_analytics)
There are a few things that need fixed. First,applymap passes each individual value for all the columns to your calling function (index_analytics). So arg1 is the individual scalar value for all the values in your dataframe. data[arg1] is always going to return a key error unless all your values are also column names.
You also shouldn't need to use apply to do this. Assuming your benchmarks are in the same dataframe then you should be able to do something like this for each benchmark. Next time include a sample of your dataframe.
df['Benchmark1_result'] = (df['Fund'] - data['Benchmark1']) / data['Benchmark1']
And if you want to calculate all the standard deviations for all the benchmarks you can do this
# assume you have a dataframe with a list of all the benchmark columns
benchmark_columns = [list, of, benchmark, columns]
np.std((df['Fund'].values - df[benchmark_columns].values) / df['Fund'].values, axis=1)
Assuming you're following the definition of Tracking Error below:
import pandas as pd
import numpy as np
# Example DataFrame
df = pd.DataFrame({'Portfolio_Returns': [5.00, 1.67], 'Bench_Returns': [2.89, .759]})
df['Active_Return'] = df['Portfolio_Returns'] - df['Bench_Returns']
print(df.head())
list_ = df['Active_Return']
temp_ = []
for val in list_:
x = val**2
temp_.append(x)
tracking_error = np.sqrt(sum(temp_))
print(f"Tracking Error is: {tracking_error}")
Or if you want it more compact (because apparently the cool kids do it):
df = pd.DataFrame({'Portfolio_Returns': [5.00, 1.67], 'Bench_Returns': [2.89, .759]})
tracking_error = np.sqrt(sum([val**2 for val in df['Portfolio_Returns'] - df['Bench_Returns']]))
print(f"Tracking Error is: {tracking_error}")
First thing first, the title is very unclear, however nothing better sprang to my mind. I'll ellaborate the problem in more detail.
I've found myself doing this routine a lot with pandas dataframes. I need to work for a while with only the part(some columns) of the DataFrame and later I want to add those columns back. The an idea came to my mind = Context Managers. But I am unable to come up with the correct implementation (if there is any..).
import pandas as pd
import numpy as np
class ProtectColumns:
def __init__(self, df, protect_cols=[]):
self.protect_cols = protect_cols
# preserve a copy of the part we want to protect
self.protected_df = df[protect_cols].copy(deep=True)
# create self.df with only the part we want to work on
self.df = df[[x for x in df.columns if x not in protect_cols]]
def __enter__(self):
# return self, or maybe only self.df?
return self
def __exit__(self, *args, **kwargs):
# btw. do i need *args and **kwargs here?
# append the preserved data back to the original, now changed
self.df[self.protect_cols] = self.protected_df
if __name__ == '__main__':
# testing
# create random DataFrame
df = pd.DataFrame(np.random.randn(6,4), columns=list("ABCD"))
# uneccessary step
df = df.applymap(lambda x: int(100 * x))
# show it
print(df)
# work without cols A and B
with ProtectColumns(df, ["A", "B"]) as PC:
# make everything 0
PC.df = PC.df.applymap(lambda x: 0)
# this prints the expected output
print(PC.df)
However, say I don't want to use PC.df onwards, but df. I could just do df = PC.df, or make a copy inside with or after that. But is is possible to handle this inside e.g. the __exit__ method?
# unchanged df
print(df)
with ProtectColumns(df, list("AB")) as PC:
PC.applymap(somefunction)
# df is now changed
print(df)
Thanks for any ideas!