जवाबों:
मार्क लुट्ज़ द्वारा "प्रोग्रामिंग पायथन" से:
curs.execute("Select * FROM people LIMIT 0")
colnames = [desc[0] for desc in curs.description]information_schema।
curs.execute("Select userId FROM people") colnames = [desc[0] for desc in curs.description] assert colnames == ['userid']
एक और चीज जो आप कर सकते हैं वह है एक कर्सर बनाना जिसके साथ आप अपने कॉलम को उनके नाम से संदर्भित कर पाएंगे (यह एक ऐसी आवश्यकता है जिसने मुझे इस पृष्ठ पर पहले स्थान पर पहुंचा दिया):
import psycopg2
from psycopg2.extras import RealDictCursor
ps_conn = psycopg2.connect(...)
ps_cursor = psql_conn.cursor(cursor_factory=RealDictCursor)
ps_cursor.execute('select 1 as col_a, 2 as col_b')
my_record = ps_cursor.fetchone()
print (my_record['col_a'],my_record['col_b'])
>> 1, 2एक अलग क्वेरी में कॉलम नाम प्राप्त करने के लिए , आप info_schema.columns तालिका को क्वेरी कर सकते हैं।
#!/usr/bin/env python3
import psycopg2
if __name__ == '__main__':
DSN = 'host=YOUR_DATABASE_HOST port=YOUR_DATABASE_PORT dbname=YOUR_DATABASE_NAME user=YOUR_DATABASE_USER'
column_names = []
with psycopg2.connect(DSN) as connection:
with connection.cursor() as cursor:
cursor.execute("select column_name from information_schema.columns where table_schema = 'YOUR_SCHEMA_NAME' and table_name='YOUR_TABLE_NAME'")
column_names = [row[0] for row in cursor]
print("Column names: {}\n".format(column_names))डेटा पंक्तियों के रूप में समान क्वेरी में स्तंभ नाम प्राप्त करने के लिए , आप कर्सर के विवरण क्षेत्र का उपयोग कर सकते हैं:
#!/usr/bin/env python3
import psycopg2
if __name__ == '__main__':
DSN = 'host=YOUR_DATABASE_HOST port=YOUR_DATABASE_PORT dbname=YOUR_DATABASE_NAME user=YOUR_DATABASE_USER'
column_names = []
data_rows = []
with psycopg2.connect(DSN) as connection:
with connection.cursor() as cursor:
cursor.execute("select field1, field2, fieldn from table1")
column_names = [desc[0] for desc in cursor.description]
for row in cursor:
data_rows.append(row)
print("Column names: {}\n".format(column_names))यदि आप db क्वेरी से नामित टपल ओब्ज होना चाहते हैं, तो आप निम्नलिखित स्निपेट का उपयोग कर सकते हैं:
from collections import namedtuple
def create_record(obj, fields):
''' given obj from db returns named tuple with fields mapped to values '''
Record = namedtuple("Record", fields)
mappings = dict(zip(fields, obj))
return Record(**mappings)
cur.execute("Select * FROM people")
colnames = [desc[0] for desc in cur.description]
rows = cur.fetchall()
cur.close()
result = []
for row in rows:
result.append(create_record(row, colnames))यह आपको रिकॉर्ड मानों तक पहुंचने की अनुमति देता है जैसे कि वे वर्ग गुण थे
record.id, record.other_table_column_name, आदि।
या उससे भी कम
from psycopg2.extras import NamedTupleCursor
with cursor(cursor_factory=NamedTupleCursor) as cur:
cur.execute("Select * ...")
return cur.fetchall()SQL क्वेरी निष्पादित करने के बाद 2.7 में लिखी गई पायथन लिपि को लिखें
total_fields = len(cursor.description)
fields_names = [i[0] for i in cursor.description
Print fields_namesमैंने देखा है कि cursor.fetchone()कॉलम की सूची cursor.description(यानी में [desc[0] for desc in curs.description]) प्राप्त करने के लिए आपको क्वेरी के बाद उपयोग करना होगा
मैं भी इसी तरह के मुद्दे का सामना करता था। मैं इसे हल करने के लिए एक सरल चाल का उपयोग करता हूं। मान लीजिए कि आपके पास किसी सूची में स्तंभ नाम हैं
col_name = ['a', 'b', 'c']फिर आप निम्नलिखित कर सकते हैं
for row in cursor.fetchone():
print zip(col_name, row) # You can use this function
def getColumns(cursorDescription):
columnList = []
for tupla in cursorDescription:
columnList.append(tupla[0])
return columnList #!/usr/bin/python
import psycopg2
#note that we have to import the Psycopg2 extras library!
import psycopg2.extras
import sys
def main():
conn_string = "host='localhost' dbname='my_database' user='postgres' password='secret'"
# print the connection string we will use to connect
print "Connecting to database\n ->%s" % (conn_string)
# get a connection, if a connect cannot be made an exception will be raised here
conn = psycopg2.connect(conn_string)
# conn.cursor will return a cursor object, you can use this query to perform queries
# note that in this example we pass a cursor_factory argument that will
# dictionary cursor so COLUMNS will be returned as a dictionary so we
# can access columns by their name instead of index.
cursor = conn.cursor(cursor_factory=psycopg2.extras.DictCursor)
# tell postgres to use more work memory
work_mem = 2048
# by passing a tuple as the 2nd argument to the execution function our
# %s string variable will get replaced with the order of variables in
# the list. In this case there is only 1 variable.
# Note that in python you specify a tuple with one item in it by placing
# a comma after the first variable and surrounding it in parentheses.
cursor.execute('SET work_mem TO %s', (work_mem,))
# Then we get the work memory we just set -> we know we only want the
# first ROW so we call fetchone.
# then we use bracket access to get the FIRST value.
# Note that even though we've returned the columns by name we can still
# access columns by numeric index as well - which is really nice.
cursor.execute('SHOW work_mem')
# Call fetchone - which will fetch the first row returned from the
# database.
memory = cursor.fetchone()
# access the column by numeric index:
# even though we enabled columns by name I'm showing you this to
# show that you can still access columns by index and iterate over them.
print "Value: ", memory[0]
# print the entire row
print "Row: ", memory
if __name__ == "__main__":
main()
curs.execute("SELECT * FROM people LIMIT 0")