How do I add a string and an int object in Python?

Question

What do I need?

I have SQL content like:

('a', 1),

So I do:

return_string = '('
    for column in columns:
        return_string += "'" + column + "', "
    return_string = return_string[:-2] + '),'
    return return_string

But it fails with the same error.

>>> a = 'a'
>>> a + 1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: cannot concatenate 'str' and 'int' objects
>>> 1 + "1"
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for +: 'int' and 'str'
>>>

However, if I convert an int into a string, everything works and I get:

('a', '1'),

But I need

('a', 1),

where 1 is unquoted '

Peter Mortensen · Accepted Answer · 2018-07-27 18:27:14Z

7

String concatenation in Python only works between strings. It doesn't infer types based on need like other languages.

There are two options, cast the integer to a strings and add it all together:

>>> x ="a"
>>> y = 1
>>> "(" + x + "," + str(y) + ")"
'(a,1)'
>>> "('" + x + "'," + str(y) + ")"
"('a',1)"
>>> "(" + repr(x) + "," + str(y) + ")"
"('a',1)"

Or use string formatting to take care of some of this behind the scenes. Either using (deprecated) "percent formatting":

>>> "(%s,%d)"%(x,y)
'(a,1)'
>>> "('%s',%d)"%(x,y)
"('a',1)"
>>> "(%s,%d)"%(repr(x),y)
"('a',1)"

Or the more standard and approved format mini-language:

>>> "({0},{1})".format(x, y)
'(a,1)'
>>> "('{0}',{1})".format(x, y)
"('a',1)"
>>> "({0},{1})".format(repr(x), y)
"('a',1)"

edited Jul 27, 2018 at 18:27

Peter Mortensen

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answered Jan 21, 2014 at 23:37

user764357

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4 Comments

user764357 Over a year ago

@KonradRudolph Percent is quicker to type and get an answer up. Once its in I always add format after (I can never remember some of the more interesting syntax of it).

mhlester Over a year ago

@KonradRudolph percent is also quicker execution!

Konrad Rudolph Over a year ago

@mhlester Do you have statistics to prove this? Even so, “correct” is better than “fast but broken”, and the documentation says specifically that “… [% substitutions] are obsolete and may go away in future versions of Python”.

mhlester Over a year ago

@KonradRudolph, yes, but hard to fit in a comment: timeit(lambda: "('%s', %d)" % ('a', 1), number=1000000) and timeit(lambda: "('{0}', {1})".format('a', 1), number=1000000) format took 35% longer. I may be mistaken but think they undepricated it for that reason.

Peter Mortensen · Accepted Answer · 2018-07-27 18:27:55Z

1

It finally clicked what you want and what your input is! It's for arbitrary length columns object! Here you go:

return_string = "(" + ', '.join((repr(column) for column in columns)) + ")"

Output is exactly as requested:

('a', 1)

All previous answers (including my deleted one), were assuming a fixed two-item input. But reading your code (and wading through the indent corruption), I see you want any columns object to be represented.

edited Jul 27, 2018 at 18:27

Peter Mortensen

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answered Jan 21, 2014 at 23:59

mhlester

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Comments

Peter Mortensen · Accepted Answer · 2018-07-27 18:29:10Z

1

You can create a function to represent your type correctly:

def toStr(x):
    if isinstance(x, int):
        return str(x)
    #another elif for others types
    else:
        return "'"+x+"'"

And use

myTuple = ('a', 1, 2, 5)
print "("+", ".join(toStr(x) for x in myTuple)+")"

to print in the correct format.

edited Jul 27, 2018 at 18:29

Peter Mortensen

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answered Jan 22, 2014 at 0:02

Victor Duarte da Silva

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Comments

Michael M. · Accepted Answer · 2024-03-27 17:56:02Z

-1

class StrInt:

    def __init__(self, strin, inte):

        self.strin = strin
        self.inte = inte
    def add(self, a, b):

       self.strin = a
       self.inte = b
       wordNum =  f"{a} {b}"
       print(wordNum)

strInt = StrInt("Word", 2)
 
strInt.add(120, "cars") 

print(type(strInt)

How many word are we talking about. I came up class which adds a word and a number using f". The function in the class adds a word and and integer.

edited Mar 27, 2024 at 17:56

Michael M.

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answered Mar 27, 2024 at 17:00

Ahmed Abdulahi Ibrahim Ahmedba

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2 Comments

Michael M. Over a year ago

Please don't stress that your answer may be wrong, it distracts from your solution. If it is wrong, then others will point it out in the comments and by voting, and you can then delete your answer if you wish.

deceze Over a year ago

The only thing of actual value here is f"{a} {b}", that class wrapper does nothing.

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