2019獨角獸企業重金招聘Python工程師標準>>>

# To see how the various functions in the DB-API work, take a look at this code,
# then the results that it prints when you press "Test Run".
#
# Then modify this code so that the student records are fetched in sorted order
# by student's name.
#

import sqlite3

# Fetch some student records from the database.
db = sqlite3.connect("students")
c = db.cursor()
query = "select name, id from students;"
c.execute(query)
rows = c.fetchall()

# First, what data structure did we get?
print "Row data:"
print rows

# And let's loop over it too:

db.close()

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# This code attempts to insert a new row into the database, but doesn't
# commit the insertion. Add a commit call in the right place to make
# it work properly.
#

import sqlite3

db = sqlite3.connect("testdb")
c = db.cursor()
c.execute("insert into balloons values ('blue', 'water') ")
db.commit()
db.close()

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子查詢

注意：先求最大值，再求平均值！！！！！！！

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# Find the players whose weight is less than the average.
#
# The function below performs two database queries in order to find the right players.
# Refactor this code so that it performs only one query.
#

def lightweights(cursor):
"""Returns a list of the players in the db whose weight is less than the average."""
cursor.execute("select avg(weight) as av from players;")
av = cursor.fetchall()[0][0] # first column of first (and only) row
cursor.execute("select name, weight from players where weight < " + str(av))
return cursor.fetchall()

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## Here's a playground to help you get a little more comfortable using DB API
## Nothing here is graded, you've done a ton of work so far and I think
## it'd be great to relax and play a bit!

## Connect to the Chinook database and try a few of your own ideas.
## This is also a great place to try experiments building queries
## for the next few quizzes!

import sqlite3

# Fetch records from either chinook.db
db = sqlite3.connect("chinook.db")
c = db.cursor()
QUERY = "SELECT * FROM Invoice;"
c.execute(QUERY)
rows = c.fetchall()

'''Uncomment to see your query in python'''
print "Row data:"
print rows

'''Uncomment to print your query by row'''
print "your output:"
for row in rows:
print " ", row[0:]

'''Uncomment to see your query as a pandas dataframe.
This is similar to the output you've been seeing throughout this course
You can learn more about pandas dataframes in our Intro to Data Analysis course!'''

import pandas as pd
df = pd.DataFrame(rows)
print df

db.close()

轉載於:https://my.oschina.net/Bettyty/blog/758105