Installing oracle odbc connection in Linux

download and unzip instantclient for Linux of basic, jdbc, odbc, sdk, sqlplus, tool into an install folder
May need tnsnames.ora and sql.ora at install_location/network/admin
export TNS_ADMIN=install_folder/network/admin
export ORACLE_HOME=install_folder
Run odbcinst -j and check if odbcinst is for local or central. If central odbcinst is required, install unixODBC at a central location.
$PATH must have the central unixODBC/bin in the head. If the local odbcinst is executed prior to the central odbcinst, local driver will be initiated
Edit unixODBC/etc/odbcinst.ini as:

[OracleDB]

Description=Oracle Unicode driver

Driver=/opt/oracle_instant_client/18.3/libsqora.so.18.1

Driver64=/opt/oracle_instant_client/18.3/libsqora.so.18.1

UsageCount=1

FileUsage=1

In Python

Install pyodbc. May need > gcc4.x. gcc8.2 works.
python3
import pyodbc
conn = pyodbc.connect("DRIVER=OracleDB; DBQ=some_name_as_shown_in_tnsnames.ora; UID=; PWD=)
cursor = conn.cursor()
cursor.execute("SELECT USERNAME FROM ALL_USERS")
ans = cursor.fetchall()
print(ans)
del(cursor)
conn.close()

In R

Install RODBC
R
library(RODBC)
conn <- odbcDriverConnect("Driver=OracleDB; Dbq=some_name_as_shown_in_tnsnames.ora; uid=; pwd=)
listSchema <- sqlQuery(conn, "SELECT USERNAME FROM ALL_USERS")
print(listSchema)
odbcClose(conn)