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map_partitions runs twice when storing dask dataframe in parquet and records are counted

I have a dask process that runs a function on each dataframe partition. I let to_parquet do the
compute() that runs the functions.
But I also need to know the number of records in the parquet table. For that, I use ddf.map_partitions(len). Problem is that when I count the number of records, a compute() is done again on the dataframe, and that makes the map_partitions functions run again.
What should be the approach to run map_partitions, save the result in parquet, and count the number of records?
def some_func(df):
df['abc'] = df['def'] * 10
return df
client = Client('127.0.0.1:8786')
ddf.map_partitions(some_func) # some_func executes twice for each partition
ddf.to_parquet('/some/folder/data', engine='pyarrow')
total = ddf.map_partitions(len).compute().sum()

One potential problem is line:
ddf.map_partitions(some_func)
Here, the instruction to dask is to map partitions, but there is no instruction to store the results of this operation. Hence, the code should probably be:
# this will store the modified dataframe as ddf
ddf = ddf.map_partitions(some_func)
Next, running .to_parquet will evaluate (compute) the dataframe ddf and discard it from memory, so the subsequent .compute will re-compute the dataframe.
This can be expensive, so some of the possible solutions are:
if ddf can fit into memory of workers, then the ddf could be persisted to avoid recomputing:
ddf = ddf.map_partitions(some_func)
ddf = ddf.persist()
ddf.to_parquet('/some/folder/data', engine='pyarrow')
total = ddf.map_partitions(len).compute().sum()
re-defining ddf in terms of computed data. Here, dask will use the stored parquet files (that were computed) and load information from them:
ddf = ddf.map_partitions(some_func)
ddf = ddf.persist()
ddf.to_parquet('/some/folder/data', engine='pyarrow')
# create a new ddf based on the computed values
ddf = dd.read_parquet('/some/folder/data')
total = ddf.map_partitions(len).compute().sum()
another solution could be to modify some_func to store the results on the fly and return len. The rough pseudocode is:
path_out = 'some/template_path/for/parquet/{number}.parquet'
def some_func(df, partition_info=None):
df['abc'] = df['def'] * 10
# this uses partition number to create an appropriate path
path_save_parquet = path_out.format(number=partition_info['number'])
df.to_parquet(path_save_parquet)
return len(df)
# this will compute total length and save the computation in the process
total = ddf.map_partitions(some_func).compute().sum()

Implementing functional programming concepts in data analysis with python and pandas

I am learning functional programming to improve my data analysis pipeline. In particular, the idea of pure functions where functions have no side effects is very useful. Also, the concept of immutable data is nice for data processing. However, I am not very sure about how to implement the concept with pandas data frames especially when we have large dataframes that we don't want to keep making copies of.
I read something about persistent data structures, but I am not sure whether it could be implemented with pandas
# Suppose we have some large dataframe
df = pd.DataFrame(some_huge_data, columns = ['column1', 'column2'])
# We want to process the data, say adding modify a column and then two columns together
def process_df(df_inside_func):
df_inside_func = \
(df_insidefunc
.assign(column1=lambda x: x.column1 + 2)
.assign(new_column=lambda x: x.column1 + x.column2)
)
return df_inside_func
# In my normal workflow
df = process_df(df)
# However in FP, I believe I should assign the output to a new variable, but the memory would double.
df_processed = process_df(df)
My current imperfect solution: keep existing columns immutable and make new column whenever column modification is implemented
df = pd.DataFrame(some_huge_data, columns = ['column1', 'column2'])
def process_df(df_inside_func):
try:
df_inside_func = df_inside_func[['column1', 'column2']]
except:
raise
df_inside_func = \
(df_insidefunc
.assign(modified_column1 = lambda x: x.column1 + 2)
.assign(new_column=lambda x: x.modified_column1 + x.column 2)
)
return df_inside_func
df = process_df(df)
Does anyone have any suggestions on a better implementation? Many thanks in advance

KeyError when reading CSV in chunks with pandas [duplicate]

I am trying to read a large csv file (aprox. 6 GB) in pandas and i am getting a memory error:
MemoryError Traceback (most recent call last)
<ipython-input-58-67a72687871b> in <module>()
----> 1 data=pd.read_csv('aphro.csv',sep=';')
...
MemoryError:
Any help on this?

The error shows that the machine does not have enough memory to read the entire
CSV into a DataFrame at one time. Assuming you do not need the entire dataset in
memory all at one time, one way to avoid the problem would be to process the CSV in
chunks (by specifying the chunksize parameter):
chunksize = 10 ** 6
for chunk in pd.read_csv(filename, chunksize=chunksize):
process(chunk)
The chunksize parameter specifies the number of rows per chunk.
(The last chunk may contain fewer than chunksize rows, of course.)
pandas >= 1.2
read_csv with chunksize returns a context manager, to be used like so:
chunksize = 10 ** 6
with pd.read_csv(filename, chunksize=chunksize) as reader:
for chunk in reader:
process(chunk)
See GH38225

Chunking shouldn't always be the first port of call for this problem.
Is the file large due to repeated non-numeric data or unwanted columns?
If so, you can sometimes see massive memory savings by reading in columns as categories and selecting required columns via pd.read_csv usecols parameter.
Does your workflow require slicing, manipulating, exporting?
If so, you can use dask.dataframe to slice, perform your calculations and export iteratively. Chunking is performed silently by dask, which also supports a subset of pandas API.
If all else fails, read line by line via chunks.
Chunk via pandas or via csv library as a last resort.

For large data l recommend you use the library "dask" e.g:
# Dataframes implement the Pandas API
import dask.dataframe as dd
df = dd.read_csv('s3://.../2018-*-*.csv')
You can read more from the documentation here.
Another great alternative would be to use modin because all the functionality is identical to pandas yet it leverages on distributed dataframe libraries such as dask.
From my projects another superior library is datatables.
# Datatable python library
import datatable as dt
df = dt.fread("s3://.../2018-*-*.csv")

I proceeded like this:
chunks=pd.read_table('aphro.csv',chunksize=1000000,sep=';',\
names=['lat','long','rf','date','slno'],index_col='slno',\
header=None,parse_dates=['date'])
df=pd.DataFrame()
%time df=pd.concat(chunk.groupby(['lat','long',chunk['date'].map(lambda x: x.year)])['rf'].agg(['sum']) for chunk in chunks)

You can read in the data as chunks and save each chunk as pickle.
import pandas as pd
import pickle
in_path = "" #Path where the large file is
out_path = "" #Path to save the pickle files to
chunk_size = 400000 #size of chunks relies on your available memory
separator = "~"
reader = pd.read_csv(in_path,sep=separator,chunksize=chunk_size,
low_memory=False)
for i, chunk in enumerate(reader):
out_file = out_path + "/data_{}.pkl".format(i+1)
with open(out_file, "wb") as f:
pickle.dump(chunk,f,pickle.HIGHEST_PROTOCOL)
In the next step you read in the pickles and append each pickle to your desired dataframe.
import glob
pickle_path = "" #Same Path as out_path i.e. where the pickle files are
data_p_files=[]
for name in glob.glob(pickle_path + "/data_*.pkl"):
data_p_files.append(name)
df = pd.DataFrame([])
for i in range(len(data_p_files)):
df = df.append(pd.read_pickle(data_p_files[i]),ignore_index=True)

I want to make a more comprehensive answer based off of the most of the potential solutions that are already provided. I also want to point out one more potential aid that may help reading process.
Option 1: dtypes
"dtypes" is a pretty powerful parameter that you can use to reduce the memory pressure of read methods. See this and this answer. Pandas, on default, try to infer dtypes of the data.
Referring to data structures, every data stored, a memory allocation takes place. At a basic level refer to the values below (The table below illustrates values for C programming language):
The maximum value of UNSIGNED CHAR = 255
The minimum value of SHORT INT = -32768
The maximum value of SHORT INT = 32767
The minimum value of INT = -2147483648
The maximum value of INT = 2147483647
The minimum value of CHAR = -128
The maximum value of CHAR = 127
The minimum value of LONG = -9223372036854775808
The maximum value of LONG = 9223372036854775807
Refer to this page to see the matching between NumPy and C types.
Let's say you have an array of integers of digits. You can both theoretically and practically assign, say array of 16-bit integer type, but you would then allocate more memory than you actually need to store that array. To prevent this, you can set dtype option on read_csv. You do not want to store the array items as long integer where actually you can fit them with 8-bit integer (np.int8 or np.uint8).
Observe the following dtype map.
Source: https://pbpython.com/pandas_dtypes.html
You can pass dtype parameter as a parameter on pandas methods as dict on read like {column: type}.
import numpy as np
import pandas as pd
df_dtype = {
"column_1": int,
"column_2": str,
"column_3": np.int16,
"column_4": np.uint8,
...
"column_n": np.float32
}
df = pd.read_csv('path/to/file', dtype=df_dtype)
Option 2: Read by Chunks
Reading the data in chunks allows you to access a part of the data in-memory, and you can apply preprocessing on your data and preserve the processed data rather than raw data. It'd be much better if you combine this option with the first one, dtypes.
I want to point out the pandas cookbook sections for that process, where you can find it here. Note those two sections there;
Reading a csv chunk-by-chunk
Reading only certain rows of a csv chunk-by-chunk
Option 3: Dask
Dask is a framework that is defined in Dask's website as:
Dask provides advanced parallelism for analytics, enabling performance at scale for the tools you love
It was born to cover the necessary parts where pandas cannot reach. Dask is a powerful framework that allows you much more data access by processing it in a distributed way.
You can use dask to preprocess your data as a whole, Dask takes care of the chunking part, so unlike pandas you can just define your processing steps and let Dask do the work. Dask does not apply the computations before it is explicitly pushed by compute and/or persist (see the answer here for the difference).
Other Aids (Ideas)
ETL flow designed for the data. Keeping only what is needed from the raw data.
First, apply ETL to whole data with frameworks like Dask or PySpark, and export the processed data.
Then see if the processed data can be fit in the memory as a whole.
Consider increasing your RAM.
Consider working with that data on a cloud platform.

Before using chunksize option if you want to be sure about the process function that you want to write inside the chunking for-loop as mentioned by #unutbu you can simply use nrows option.
small_df = pd.read_csv(filename, nrows=100)
Once you are sure that the process block is ready, you can put that in the chunking for loop for the entire dataframe.

The function read_csv and read_table is almost the same. But you must assign the delimiter “，” when you use the function read_table in your program.
def get_from_action_data(fname, chunk_size=100000):
reader = pd.read_csv(fname, header=0, iterator=True)
chunks = []
loop = True
while loop:
try:
chunk = reader.get_chunk(chunk_size)[["user_id", "type"]]
chunks.append(chunk)
except StopIteration:
loop = False
print("Iteration is stopped")
df_ac = pd.concat(chunks, ignore_index=True)

Solution 1:
Using pandas with large data
Solution 2:
TextFileReader = pd.read_csv(path, chunksize=1000) # the number of rows per chunk
dfList = []
for df in TextFileReader:
dfList.append(df)
df = pd.concat(dfList,sort=False)

Here follows an example:
chunkTemp = []
queryTemp = []
query = pd.DataFrame()
for chunk in pd.read_csv(file, header=0, chunksize=<your_chunksize>, iterator=True, low_memory=False):
#REPLACING BLANK SPACES AT COLUMNS' NAMES FOR SQL OPTIMIZATION
chunk = chunk.rename(columns = {c: c.replace(' ', '') for c in chunk.columns})
#YOU CAN EITHER:
#1)BUFFER THE CHUNKS IN ORDER TO LOAD YOUR WHOLE DATASET
chunkTemp.append(chunk)
#2)DO YOUR PROCESSING OVER A CHUNK AND STORE THE RESULT OF IT
query = chunk[chunk[<column_name>].str.startswith(<some_pattern>)]
#BUFFERING PROCESSED DATA
queryTemp.append(query)
#! NEVER DO pd.concat OR pd.DataFrame() INSIDE A LOOP
print("Database: CONCATENATING CHUNKS INTO A SINGLE DATAFRAME")
chunk = pd.concat(chunkTemp)
print("Database: LOADED")
#CONCATENATING PROCESSED DATA
query = pd.concat(queryTemp)
print(query)

You can try sframe, that have the same syntax as pandas but allows you to manipulate files that are bigger than your RAM.

If you use pandas read large file into chunk and then yield row by row, here is what I have done
import pandas as pd
def chunck_generator(filename, header=False,chunk_size = 10 ** 5):
for chunk in pd.read_csv(filename,delimiter=',', iterator=True, chunksize=chunk_size, parse_dates=[1] ):
yield (chunk)
def _generator( filename, header=False,chunk_size = 10 ** 5):
chunk = chunck_generator(filename, header=False,chunk_size = 10 ** 5)
for row in chunk:
yield row
if __name__ == "__main__":
filename = r'file.csv'
generator = generator(filename=filename)
while True:
print(next(generator))

In case someone is still looking for something like this, I found that this new library called modin can help. It uses distributed computing that can help with the read. Here's a nice article comparing its functionality with pandas. It essentially uses the same functions as pandas.
import modin.pandas as pd
pd.read_csv(CSV_FILE_NAME)

If you have csv file with millions of data entry and you want to load full dataset you should use dask_cudf,
import dask_cudf as dc
df = dc.read_csv("large_data.csv")

In addition to the answers above, for those who want to process CSV and then export to csv, parquet or SQL, d6tstack is another good option. You can load multiple files and it deals with data schema changes (added/removed columns). Chunked out of core support is already built in.
def apply(dfg):
# do stuff
return dfg
c = d6tstack.combine_csv.CombinerCSV([bigfile.csv], apply_after_read=apply, sep=',', chunksize=1e6)
# or
c = d6tstack.combine_csv.CombinerCSV(glob.glob('*.csv'), apply_after_read=apply, chunksize=1e6)
# output to various formats, automatically chunked to reduce memory consumption
c.to_csv_combine(filename='out.csv')
c.to_parquet_combine(filename='out.pq')
c.to_psql_combine('postgresql+psycopg2://usr:pwd#localhost/db', 'tablename') # fast for postgres
c.to_mysql_combine('mysql+mysqlconnector://usr:pwd#localhost/db', 'tablename') # fast for mysql
c.to_sql_combine('postgresql+psycopg2://usr:pwd#localhost/db', 'tablename') # slow but flexible

How to implement dask mappartitions on multiple dataframe lambda function?

I've implemented a fuzzy string matching algo between two dataframes just using pandas. My issue is how do I convert this to a dask operation using multiple cores? My program runs about 3-4 days on pure python, and I want to parallelize the operations to optimize time cost. I've already used the multiprocessing package to extract the number of cores using the code below:
numCores = multiprocessing.cpu_count()
fields = ['id','phase','new']
emb = pd.read_csv('my_csv.csv', skipinitialspace=True, usecols=fields)
Then I had to subdivide the dataframe emb into two dataframes (emb1, emb2) based on numeric values associated per string. As in I'm matching a dataframe with all elements having value to 3 to their corresponding value 2 in the other dataframe by matched string.The code for pure pandas operation is below.
emb1 = emb[emb.phase.isin([3.0])]
emb1.set_index('id',inplace=True)
emb2 = emb[emb.phase.isin([2.0,1.5])]
emb2.set_index('id',inplace=True)
def fuzzy_match(x, choices, scorer, cutoff):
return process.extractOne(x, choices=choices, scorer=scorer, score_cutoff=cutoff)
FuzzyWuzzyResults = pd.DataFrame(emb1.sort_index().loc[:,'strings'].apply(fuzzy_match, args = (emb2.loc[:,'strings'],fuzz.ratio,90)))
I sort of tried doing a dask implementation using this code:
emb1 = dd.from_pandas(emb1, npartitions=numCores)
emb2 = dd.from_pandas(emb2, npartitions=numCores)
But running the lambda function for two dataframes is confusing me. Any ideas?

So I just fixed my code to remove the manual partition of the dataframe and used groupby instead.
Here's the code:
for i in [2.0,1.5]:
FuzzyWuzzyResults = emb.map_partitions(lambda df: df.groupby('phase').get_group(3.0)['drugs'].apply(fuzzy_match, args=(df.groupby('phase').get_group(i)['drugs'],fuzz.ratio,90)), meta=('results')).compute()
Not sure whether it's accurate, but at least it's running, and that too on all CPU cores.

How to read a large csv and write it again using a Dataframe in Pandas? [duplicate]

I am trying to read a large csv file (aprox. 6 GB) in pandas and i am getting a memory error:
MemoryError Traceback (most recent call last)
<ipython-input-58-67a72687871b> in <module>()
----> 1 data=pd.read_csv('aphro.csv',sep=';')
...
MemoryError:
Any help on this?

The error shows that the machine does not have enough memory to read the entire
CSV into a DataFrame at one time. Assuming you do not need the entire dataset in
memory all at one time, one way to avoid the problem would be to process the CSV in
chunks (by specifying the chunksize parameter):
chunksize = 10 ** 6
for chunk in pd.read_csv(filename, chunksize=chunksize):
process(chunk)
The chunksize parameter specifies the number of rows per chunk.
(The last chunk may contain fewer than chunksize rows, of course.)
pandas >= 1.2
read_csv with chunksize returns a context manager, to be used like so:
chunksize = 10 ** 6
with pd.read_csv(filename, chunksize=chunksize) as reader:
for chunk in reader:
process(chunk)
See GH38225

Chunking shouldn't always be the first port of call for this problem.
Is the file large due to repeated non-numeric data or unwanted columns?
If so, you can sometimes see massive memory savings by reading in columns as categories and selecting required columns via pd.read_csv usecols parameter.
Does your workflow require slicing, manipulating, exporting?
If so, you can use dask.dataframe to slice, perform your calculations and export iteratively. Chunking is performed silently by dask, which also supports a subset of pandas API.
If all else fails, read line by line via chunks.
Chunk via pandas or via csv library as a last resort.

For large data l recommend you use the library "dask" e.g:
# Dataframes implement the Pandas API
import dask.dataframe as dd
df = dd.read_csv('s3://.../2018-*-*.csv')
You can read more from the documentation here.
Another great alternative would be to use modin because all the functionality is identical to pandas yet it leverages on distributed dataframe libraries such as dask.
From my projects another superior library is datatables.
# Datatable python library
import datatable as dt
df = dt.fread("s3://.../2018-*-*.csv")

I proceeded like this:
chunks=pd.read_table('aphro.csv',chunksize=1000000,sep=';',\
names=['lat','long','rf','date','slno'],index_col='slno',\
header=None,parse_dates=['date'])
df=pd.DataFrame()
%time df=pd.concat(chunk.groupby(['lat','long',chunk['date'].map(lambda x: x.year)])['rf'].agg(['sum']) for chunk in chunks)

You can read in the data as chunks and save each chunk as pickle.
import pandas as pd
import pickle
in_path = "" #Path where the large file is
out_path = "" #Path to save the pickle files to
chunk_size = 400000 #size of chunks relies on your available memory
separator = "~"
reader = pd.read_csv(in_path,sep=separator,chunksize=chunk_size,
low_memory=False)
for i, chunk in enumerate(reader):
out_file = out_path + "/data_{}.pkl".format(i+1)
with open(out_file, "wb") as f:
pickle.dump(chunk,f,pickle.HIGHEST_PROTOCOL)
In the next step you read in the pickles and append each pickle to your desired dataframe.
import glob
pickle_path = "" #Same Path as out_path i.e. where the pickle files are
data_p_files=[]
for name in glob.glob(pickle_path + "/data_*.pkl"):
data_p_files.append(name)
df = pd.DataFrame([])
for i in range(len(data_p_files)):
df = df.append(pd.read_pickle(data_p_files[i]),ignore_index=True)

I want to make a more comprehensive answer based off of the most of the potential solutions that are already provided. I also want to point out one more potential aid that may help reading process.
Option 1: dtypes
"dtypes" is a pretty powerful parameter that you can use to reduce the memory pressure of read methods. See this and this answer. Pandas, on default, try to infer dtypes of the data.
Referring to data structures, every data stored, a memory allocation takes place. At a basic level refer to the values below (The table below illustrates values for C programming language):
The maximum value of UNSIGNED CHAR = 255
The minimum value of SHORT INT = -32768
The maximum value of SHORT INT = 32767
The minimum value of INT = -2147483648
The maximum value of INT = 2147483647
The minimum value of CHAR = -128
The maximum value of CHAR = 127
The minimum value of LONG = -9223372036854775808
The maximum value of LONG = 9223372036854775807
Refer to this page to see the matching between NumPy and C types.
Let's say you have an array of integers of digits. You can both theoretically and practically assign, say array of 16-bit integer type, but you would then allocate more memory than you actually need to store that array. To prevent this, you can set dtype option on read_csv. You do not want to store the array items as long integer where actually you can fit them with 8-bit integer (np.int8 or np.uint8).
Observe the following dtype map.
Source: https://pbpython.com/pandas_dtypes.html
You can pass dtype parameter as a parameter on pandas methods as dict on read like {column: type}.
import numpy as np
import pandas as pd
df_dtype = {
"column_1": int,
"column_2": str,
"column_3": np.int16,
"column_4": np.uint8,
...
"column_n": np.float32
}
df = pd.read_csv('path/to/file', dtype=df_dtype)
Option 2: Read by Chunks
Reading the data in chunks allows you to access a part of the data in-memory, and you can apply preprocessing on your data and preserve the processed data rather than raw data. It'd be much better if you combine this option with the first one, dtypes.
I want to point out the pandas cookbook sections for that process, where you can find it here. Note those two sections there;
Reading a csv chunk-by-chunk
Reading only certain rows of a csv chunk-by-chunk
Option 3: Dask
Dask is a framework that is defined in Dask's website as:
Dask provides advanced parallelism for analytics, enabling performance at scale for the tools you love
It was born to cover the necessary parts where pandas cannot reach. Dask is a powerful framework that allows you much more data access by processing it in a distributed way.
You can use dask to preprocess your data as a whole, Dask takes care of the chunking part, so unlike pandas you can just define your processing steps and let Dask do the work. Dask does not apply the computations before it is explicitly pushed by compute and/or persist (see the answer here for the difference).
Other Aids (Ideas)
ETL flow designed for the data. Keeping only what is needed from the raw data.
First, apply ETL to whole data with frameworks like Dask or PySpark, and export the processed data.
Then see if the processed data can be fit in the memory as a whole.
Consider increasing your RAM.
Consider working with that data on a cloud platform.

Before using chunksize option if you want to be sure about the process function that you want to write inside the chunking for-loop as mentioned by #unutbu you can simply use nrows option.
small_df = pd.read_csv(filename, nrows=100)
Once you are sure that the process block is ready, you can put that in the chunking for loop for the entire dataframe.

The function read_csv and read_table is almost the same. But you must assign the delimiter “，” when you use the function read_table in your program.
def get_from_action_data(fname, chunk_size=100000):
reader = pd.read_csv(fname, header=0, iterator=True)
chunks = []
loop = True
while loop:
try:
chunk = reader.get_chunk(chunk_size)[["user_id", "type"]]
chunks.append(chunk)
except StopIteration:
loop = False
print("Iteration is stopped")
df_ac = pd.concat(chunks, ignore_index=True)

Solution 1:
Using pandas with large data
Solution 2:
TextFileReader = pd.read_csv(path, chunksize=1000) # the number of rows per chunk
dfList = []
for df in TextFileReader:
dfList.append(df)
df = pd.concat(dfList,sort=False)

Here follows an example:
chunkTemp = []
queryTemp = []
query = pd.DataFrame()
for chunk in pd.read_csv(file, header=0, chunksize=<your_chunksize>, iterator=True, low_memory=False):
#REPLACING BLANK SPACES AT COLUMNS' NAMES FOR SQL OPTIMIZATION
chunk = chunk.rename(columns = {c: c.replace(' ', '') for c in chunk.columns})
#YOU CAN EITHER:
#1)BUFFER THE CHUNKS IN ORDER TO LOAD YOUR WHOLE DATASET
chunkTemp.append(chunk)
#2)DO YOUR PROCESSING OVER A CHUNK AND STORE THE RESULT OF IT
query = chunk[chunk[<column_name>].str.startswith(<some_pattern>)]
#BUFFERING PROCESSED DATA
queryTemp.append(query)
#! NEVER DO pd.concat OR pd.DataFrame() INSIDE A LOOP
print("Database: CONCATENATING CHUNKS INTO A SINGLE DATAFRAME")
chunk = pd.concat(chunkTemp)
print("Database: LOADED")
#CONCATENATING PROCESSED DATA
query = pd.concat(queryTemp)
print(query)

You can try sframe, that have the same syntax as pandas but allows you to manipulate files that are bigger than your RAM.

If you use pandas read large file into chunk and then yield row by row, here is what I have done
import pandas as pd
def chunck_generator(filename, header=False,chunk_size = 10 ** 5):
for chunk in pd.read_csv(filename,delimiter=',', iterator=True, chunksize=chunk_size, parse_dates=[1] ):
yield (chunk)
def _generator( filename, header=False,chunk_size = 10 ** 5):
chunk = chunck_generator(filename, header=False,chunk_size = 10 ** 5)
for row in chunk:
yield row
if __name__ == "__main__":
filename = r'file.csv'
generator = generator(filename=filename)
while True:
print(next(generator))

In case someone is still looking for something like this, I found that this new library called modin can help. It uses distributed computing that can help with the read. Here's a nice article comparing its functionality with pandas. It essentially uses the same functions as pandas.
import modin.pandas as pd
pd.read_csv(CSV_FILE_NAME)

If you have csv file with millions of data entry and you want to load full dataset you should use dask_cudf,
import dask_cudf as dc
df = dc.read_csv("large_data.csv")

In addition to the answers above, for those who want to process CSV and then export to csv, parquet or SQL, d6tstack is another good option. You can load multiple files and it deals with data schema changes (added/removed columns). Chunked out of core support is already built in.
def apply(dfg):
# do stuff
return dfg
c = d6tstack.combine_csv.CombinerCSV([bigfile.csv], apply_after_read=apply, sep=',', chunksize=1e6)
# or
c = d6tstack.combine_csv.CombinerCSV(glob.glob('*.csv'), apply_after_read=apply, chunksize=1e6)
# output to various formats, automatically chunked to reduce memory consumption
c.to_csv_combine(filename='out.csv')
c.to_parquet_combine(filename='out.pq')
c.to_psql_combine('postgresql+psycopg2://usr:pwd#localhost/db', 'tablename') # fast for postgres
c.to_mysql_combine('mysql+mysqlconnector://usr:pwd#localhost/db', 'tablename') # fast for mysql
c.to_sql_combine('postgresql+psycopg2://usr:pwd#localhost/db', 'tablename') # slow but flexible