How to construct a list as (key,value) pairs with PyMySQL and Python?
I have the following code:
connection = pymysql.connect(...)
try:
with connection.cursor() as cursor:
sql = "select cola,colb from ...."
result = cursor.fetchall()
How to build a list from the result?
finally:
connection.close()
The query returns data as:
cola colb
-----------
123 abc
124 abd
140 ghf
cola is the key
colb is the value
I know it should be something like:
list =
for i in range (0, ????):
cola_value = result[0][i].get('cola')
colb_value = result[1][i].get('colb')
list.append((cola_value, colb_value))
I'm wondering what is the correct syntax and if this is the correct approach?
I want to be able to search the list by key and access the value by key.
I'll need 2-3 lists each one with around 900000 (key,value) pairs.
Is it smart to manage it in memory or better to write it to file and process it on disk?
python pymysql
asked Nov 12 '18 at 13:10
Luis
949
add a comment |
I have the following code:
connection = pymysql.connect(...)
try:
with connection.cursor() as cursor:
sql = "select cola,colb from ...."
result = cursor.fetchall()
How to build a list from the result?
finally:
connection.close()
The query returns data as:
cola colb
-----------
123 abc
124 abd
140 ghf
cola is the key
colb is the value
I know it should be something like:
list =
for i in range (0, ????):
cola_value = result[0][i].get('cola')
colb_value = result[1][i].get('colb')
list.append((cola_value, colb_value))
I'm wondering what is the correct syntax and if this is the correct approach?
I want to be able to search the list by key and access the value by key.
I'll need 2-3 lists each one with around 900000 (key,value) pairs.
Is it smart to manage it in memory or better to write it to file and process it on disk?
python pymysql
asked Nov 12 '18 at 13:10
Luis
949
add a comment |
I have the following code:
connection = pymysql.connect(...)
try:
with connection.cursor() as cursor:
sql = "select cola,colb from ...."
result = cursor.fetchall()
How to build a list from the result?
finally:
connection.close()
The query returns data as:
cola colb
-----------
123 abc
124 abd
140 ghf
cola is the key
colb is the value
I know it should be something like:
list =
for i in range (0, ????):
cola_value = result[0][i].get('cola')
colb_value = result[1][i].get('colb')
list.append((cola_value, colb_value))
I'm wondering what is the correct syntax and if this is the correct approach?
I want to be able to search the list by key and access the value by key.
I'll need 2-3 lists each one with around 900000 (key,value) pairs.
Is it smart to manage it in memory or better to write it to file and process it on disk?
python pymysql
asked Nov 12 '18 at 13:10
Luis
949
I have the following code:
connection = pymysql.connect(...)
try:
with connection.cursor() as cursor:
sql = "select cola,colb from ...."
result = cursor.fetchall()
How to build a list from the result?
finally:
connection.close()
The query returns data as:
cola colb
-----------
123 abc
124 abd
140 ghf
cola is the key
colb is the value
I know it should be something like:
list =
for i in range (0, ????):
cola_value = result[0][i].get('cola')
colb_value = result[1][i].get('colb')
list.append((cola_value, colb_value))
I'm wondering what is the correct syntax and if this is the correct approach?
I want to be able to search the list by key and access the value by key.
I'll need 2-3 lists each one with around 900000 (key,value) pairs.
Is it smart to manage it in memory or better to write it to file and process it on disk?
python pymysql
python pymysql
asked Nov 12 '18 at 13:10
Luis
949
asked Nov 12 '18 at 13:10
Luis
949
asked Nov 12 '18 at 13:10
Luis
949
asked Nov 12 '18 at 13:10
Luis
949
asked Nov 12 '18 at 13:10
Luis
949
949
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
I did not try this, but you should be able to use a list comprehension:
list = [(r['cola'], r['colb']) for r in result]
If you plan to do lookups by key, using a dictionary would be even better:
map = {r['cola']: r['colb'] for r in result}
Then if you want to find the value corresponding with they key 123:
value = map[123]
Regarding whether or not it makes sense to hold 900,000 pairs depends on your hardware resources - there are probably more memory efficient ways to do it, but you might need to install some additional dependencies.
answered Nov 12 '18 at 13:30
shevron
1,7191323
just edited your answer to .get('cola')
– Luis
Nov 12 '18 at 13:51
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
I did not try this, but you should be able to use a list comprehension:
list = [(r['cola'], r['colb']) for r in result]
If you plan to do lookups by key, using a dictionary would be even better:
map = {r['cola']: r['colb'] for r in result}
Then if you want to find the value corresponding with they key 123:
value = map[123]
Regarding whether or not it makes sense to hold 900,000 pairs depends on your hardware resources - there are probably more memory efficient ways to do it, but you might need to install some additional dependencies.
answered Nov 12 '18 at 13:30
shevron
1,7191323
just edited your answer to .get('cola')
– Luis
Nov 12 '18 at 13:51
add a comment |
I did not try this, but you should be able to use a list comprehension:
list = [(r['cola'], r['colb']) for r in result]
If you plan to do lookups by key, using a dictionary would be even better:
map = {r['cola']: r['colb'] for r in result}
Then if you want to find the value corresponding with they key 123:
value = map[123]
Regarding whether or not it makes sense to hold 900,000 pairs depends on your hardware resources - there are probably more memory efficient ways to do it, but you might need to install some additional dependencies.
answered Nov 12 '18 at 13:30
shevron
1,7191323
just edited your answer to .get('cola')
– Luis
Nov 12 '18 at 13:51
add a comment |
I did not try this, but you should be able to use a list comprehension:
list = [(r['cola'], r['colb']) for r in result]
If you plan to do lookups by key, using a dictionary would be even better:
map = {r['cola']: r['colb'] for r in result}
Then if you want to find the value corresponding with they key 123:
value = map[123]
Regarding whether or not it makes sense to hold 900,000 pairs depends on your hardware resources - there are probably more memory efficient ways to do it, but you might need to install some additional dependencies.
answered Nov 12 '18 at 13:30
shevron
1,7191323
I did not try this, but you should be able to use a list comprehension:
list = [(r['cola'], r['colb']) for r in result]
If you plan to do lookups by key, using a dictionary would be even better:
map = {r['cola']: r['colb'] for r in result}
Then if you want to find the value corresponding with they key 123:
value = map[123]
Regarding whether or not it makes sense to hold 900,000 pairs depends on your hardware resources - there are probably more memory efficient ways to do it, but you might need to install some additional dependencies.
answered Nov 12 '18 at 13:30
shevron
1,7191323
answered Nov 12 '18 at 13:30
shevron
1,7191323
answered Nov 12 '18 at 13:30
shevron
1,7191323
answered Nov 12 '18 at 13:30
shevron
1,7191323
1,7191323
just edited your answer to .get('cola')
– Luis
Nov 12 '18 at 13:51
add a comment |
just edited your answer to .get('cola')
– Luis
Nov 12 '18 at 13:51
just edited your answer to .get('cola')
– Luis
Nov 12 '18 at 13:51
just edited your answer to .get('cola')
– Luis
Nov 12 '18 at 13:51
add a comment |
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