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Trimming a huge (3.5 GB) csv file to read into R
...short, it's huge, and it's not going to fit into memory if I try to simply read it.
13 Answers
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Read a variable in bash with a default value
I need to read a value from the terminal in a bash script. I would like to be able to provide a default value that the user can change.
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Create Pandas DataFrame from a string
...IO.StringIO (python2) or io.StringIO (python3) and pass that to the pandas.read_csv function. E.g:
import sys
if sys.version_info[0] < 3:
from StringIO import StringIO
else:
from io import StringIO
import pandas as pd
TESTDATA = StringIO("""col1;col2;col3
1;4.4;99
2;4.5;200
...
Read file line by line using ifstream in C++
...standard methods are:
Assume that every line consists of two numbers and read token by token:
int a, b;
while (infile >> a >> b)
{
// process pair (a,b)
}
Line-based parsing, using string streams:
#include <sstream>
#include <string>
std::string line;
while (std::ge...
How to debug Lock wait timeout exceeded on MySQL?
...Transaction:
TRANSACTION 0 606162814, ACTIVE 0 sec, process no 29956, OS thread id 1223895360 updating or deleting, thread declared inside InnoDB 499
mysql tables in use 1, locked 1
14 lock struct(s), heap size 3024, 8 row lock(s), undo log entries 1
MySQL thread id 3686635, query id 124164167 10.64...
Split string into an array in Bash
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IFS=', ' read -r -a array <<< "$string"
Note that the characters in $IFS are treated individually as separators so that in this case fields may be separated by either a comma or a space rather than the sequence of the two c...
Why is the gets function so dangerous that it should not be used?
... use gets safely, you have to know exactly how many characters you will be reading, so that you can make your buffer large enough. You will only know that if you know exactly what data you will be reading.
Instead of using gets, you want to use fgets, which has the signature
char* fgets(char *stri...
Any way to select without causing locking in MySQL?
...ck)
and the MYSQL equivalent is
SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED ;
SELECT * FROM TABLE_NAME ;
SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ ;
EDIT
Michael Mior suggested the following (from the comments)
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED ;
SELE...
How to read a file without newlines?
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You can read the whole file and split lines using str.splitlines:
temp = file.read().splitlines()
Or you can strip the newline by hand:
temp = [line[:-1] for line in file]
Note: this last solution only works if the file ends wi...
Read only file system on Android
...following error: failed to copy 'c:\build.prop' to '/system//build.prop': Read-only file system .
24 Answers
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