三引号内的 Python 参数

Question

I have a python script that contains a sql query. I use triple quotes around the sql query for formatting purposes. I'd like to inject variables that I populate from the command line into the query. How can I do this while preserving the triple quotes. Are there better ways to get around the triple quotes?

Ex:

AGE = raw_input("Enter your age: ")

vdf = vertica.select_dataframe("""
    Select
        col1
        col2
        coln
    FROM
        TableX
    WHERE
        col2 IN (21, 22, AGE)
    Group BY 1
""")

Answer 1

You can use format like this:

AGE = raw_input("Enter your age: ")
query_1 = """
    Select
        col1
        col2
        coln
    FROM
        TableX
    WHERE
        col2 IN (21, 22, {})
    Group BY 1
"""
vdf = vertica.select_dataframe(query_1.format(AGE))

A simple example with triple quotes and multiple assignments is:

>>> age = 100
>>> name = "koukouviou"
>>> """I am {} and I am {} years old""".format(name, age)
'I am koukouviou and I am 100 years old'

Answer 2

You could make the query string separate and use format to put correct age, eg:

a_query = """
    Select
        col1
        col2
        coln
    FROM
        TableX
    WHERE
        col2 IN (21, 22, {})
    Group BY 1
"""

vdf = vertica.select_dataframe(a_query.format(AGE))

Answer 3

I am surprised, that the fabulous % operator is not mentioned, pythons build in string formatting would make your original lines work with a tiny modification:

AGE = raw_input("Enter your age: ")

vdf = vertica.select_dataframe("""
    Select
        col1,
        col2,
        coln
    FROM
        TableX
    WHERE
        col2 IN (21, 22, %s)
    Group BY 1
""" % AGE)

This would also work for queries with multiple arguments:

AGE = raw_input("Enter your age: ")
GENDER = raw_input("Enter your gender (m/f): ")
HEIGHT = raw_input("Enter your height in cm: ")

vdf = vertica.select_dataframe("""
    INSERT INTO stats (
        age,
        gender,
        height
    )
    VALUES
    (
        '%s',
        '%s',
        '%s'
    )
""" % ( AGE, GENDER, HEIGHT ))

Answer 4

I will add one more answer with a dict unpacking as it made my life much simpler. Using @hexerei-software's INSERT example:

AGE = raw_input("Enter your age: ")
GENDER = raw_input("Enter your gender (m/f): ")
HEIGHT = raw_input("Enter your height in cm: ")

settings = {'AGE': AGE, 'GENDER': GENDER, 'HEIGHT': HEIGHT}

vdf = vertica.select_dataframe("""
    INSERT INTO stats (
        age,
        gender,
        height
    )
    VALUES
    (
        '{AGE}',
        '{GENDER}',
        '{HEIGHT}'
    )
""".format(**settings))

Answer 5

I prefer using f-Strings !

vdf = vertica.select_dataframe(f"""
    Select
        col1
        col2
        coln
    FROM
        TableX
    WHERE
        col2 IN (21, 22, {AGE})
    Group BY 1
""")