pandas 生成器，生成大数据

1.先说下常规思路：

写追加模式，第一次写入头header,第二次开始：header =None

 2.后来想了下，还是不够灵敏：id列不够随意，就用生成器来yield，不断批量batch_size 内存生成就返回，避免Memory Error:

d分两步：

第一步：

唯一id列：10w，sha256加密：

import csv
import uuid
from hashlib import sha256
import numpy as np
import argparse
import random,string


def gen_demo(rows:int, each_iter:int, features,mode_encrypt:int):
    """yield one batch_size data by each_iter size in case memory leak """
    capacity = []
    counter = 0
    for i in range(rows):
        temp = []
        uid = str(uuid.uuid1()).replace("-", "")
        if mode_encrypt:
            encrypt = sha256(uid.encode("utf-8")).hexdigest()
        else:
            encrypt=uid+str(''.join(random.sample(string.ascii_letters+string.digits,10)))
        if not features:
            temp.append(encrypt)
        else:
            feature_value = np.around(np.random.normal(0, 1, features), decimals=5, out=None).tolist()
            one_data = [encrypt] + feature_value

            temp.extend(one_data)
        capacity.append(temp)
        counter += 1
        if counter % each_iter == 0:
            print(f" has gen {counter} data")
            pass

    yield capacity


def foo():
    """ example: python  generate_id.py -r 100000 -b 10000 -e 1"""
    parse = argparse.ArgumentParser()
    parse.add_argument("-e","--encrypt",type=int,required=True,help="encrypt 0 mean false,1 mean true ")
    parse.add_argument("-r","--row",required=True,type=int,help="rows of samples")
    parse.add_argument("-f","--features",required=False,type=int,help="number of cols generate features,if -f generate,else false")
    parse.add_argument("-b","--batch_size",required=True,type=int,help="number of each time yield sample batch_size ")
    parse.add_argument("-header","--header",required=False,type=bool,help="if generate header or not true mean yes, false no ")
    parse.add_argument("-n","--name",required=False,type=str,help="the name of save output_data csv")
    args = parse.parse_args()
    if args.features:
        features=args.features
    else:
        features=0
    row = args.row
    each_iter =args.batch_size

    if args.name:
        name=args.name
        print("args name is %s"%name)
    else:
        name="id_sha256"
    if args.header and features:
        header = ["id"] + [f"x{i}" for i in range(features)]
    else:
        header=None  # TODO if you want keep id_csv with id header, you  can setting header=["id"]
    encrypt_method=args.encrypt
    data=gen_demo(row, each_iter, features, encrypt_method)
    with open("./%s.csv"%name, "w", newline="")as f:
        wr = csv.writer(f)
        if header:
            wr.writerow(header)
        for dt in data:
            wr.writerows(dt)


if __name__ == '__main__':
    print("tip:\n",foo.__doc__)
    foo()

第二步：generate data and write to csv :

import pandas as pd
import numpy as np
import csv
from threading import Lock,RLock
lock=RLock()
# TODO __author__ ="Chen"
""">>>>10wx1000columns cost 143.43s <<<<< 10wx10columns cost 2.02s"""
# 特征列
col = 10

# generate samples rows numbers,must be the same with id_sha256.csv id rows
totals_row = 100000

# 每次yield分批的写入save_data output数量样本,suggest 2000 or 5000 or 10000 ,
batch_size = 10000

# data_output path for guest or host  data_set
target_path = "./breast_b.csv"

# id_csv path
id_csv_path = "./id_sha256.csv"

# id_csv_path = "./ids_1sw.csv" # todo test id range(100000) int64

# with label,生成数据是否带有label
label_switch=True

if batch_size > totals_row:
    raise ValueError(f"batch_size number can't more than samples")


def yield_id():
    data_set = pd.read_csv(id_csv_path, chunksize=batch_size, iterator=True, header=None)
    counter = 0
    for it in data_set:
        size = it.shape[0]
        # print(f"yield id size is {size}")
        a = list(map(lambda x: x[0], it.values.tolist()))
        counter += size
        print(f" has gen {counter} data")
        yield a


def concat(with_label):
    ids = yield_id()
    for id_list in ids:  # todo len(id_list)=batch_size
        df_id = pd.DataFrame(id_list,columns=["id"],dtype=np.str)
        value_a=np.around(np.random.normal(0, 1, (batch_size, col)), decimals=5, out=None)
        df_feature = pd.DataFrame(value_a,columns=[f"x{i}" for i in range(col)])
        if with_label:
            df_y = pd.DataFrame(np.random.choice(2, batch_size),dtype=np.int64,columns=["y"])
            one_iter_data = pd.concat([df_id,df_y, df_feature], axis=1,ignore_index=False)#.values.tolist()
        else:
            one_iter_data = pd.concat([df_id, df_feature], axis=1,ignore_index=False)#.values.tolist()
        yield one_iter_data



def save_data(path,with_label):
    """ if with label then generate dataout_put.csv  with label y
    feature_list = [f"x{i}" for i in range(col)]
    if with_label:
        header = ["id"] +['y']+ feature_list
    else:
        header = ["id"] + feature_list
    <<<<
        # with open(path, "w", newline="")as f:
    #     wr = csv.writer(f)
    #     if header:
    #         wr.writerow(header)
    #     for dt in one_batch:
    #         wr.writerows(dt)
    """
    one_batch = concat(with_label)
    for index,df_dt in enumerate(one_batch):
        if index==0:
            print(df_dt.dtypes,"\n")
            print(f"header of csv:\n{df_dt.columns.values.tolist()}")
            df_dt.to_csv(path,index=False)
        else:
            df_dt.to_csv(path,index=False,mode="a",header=None)




if __name__ == '__main__':
    """
    before you generate data_output.csv to $target_path,you should run generate_id.py 
    to gen $totals_row numbers of id.then execute 'python  generate_id.py -r 100000 -b 10000 -e 1' to gen data_output
    """
    import time
    start=time.time()
    idsha256=pd.read_csv(id_csv_path,header=None)
    id_sha256_rows=idsha256.shape[0]
    if totals_row == id_sha256_rows:
        pass
    else:
        raise ValueError(f"Sample total rows is {totals_row} must be the same with id_sha256.csv id rows size:{id_sha256_rows}")
    save_data(target_path,with_label=label_switch)

    print(time.time()-start)

　测试了下：10wx10 column cost 2 s.