Python strings and integer concatenation

Question

I want to create a string using an integer appended to it, in a for loop. Like this:

for i in range(1, 11):
  string = "string" + i

But it returns an error:

TypeError: unsupported operand type(s) for +: 'int' and 'str'

What's the best way to concatenate the string and integer?

Your question is unclear. What is it the output you want to get? `string = "string10"`? `string = "string1string2string3string4string5string6string7string8string9string10"`? Ten different variables? — badp, May 17 '10 at 08:11
@michele Any chance you can change the accepted answer on this question? Backticks are deprecated and should not be used. — Roger Fan, Oct 03 '14 at 16:39
Sorry, I'm reading answers and I find it all so so weird, just do this and end with this: for i in range(1,11): string += str(i) — Windgate, Mar 23 '21 at 21:03

score 313 · Accepted Answer · edited Apr 03 '22 at 18:07

313

NOTE:

The method used in this answer (backticks) is deprecated in later versions of Python 2, and removed in Python 3. Use the str() function instead.

You can use:

string = 'string'
for i in range(11):
    string +=`i`
print string

It will print string012345678910.

To get string0, string1 ..... string10 you can use this as YOU suggested:

>>> string = "string"
>>> [string+`i` for i in range(11)]

For Python 3

You can use:

string = 'string'
for i in range(11):
    string += str(i)
print string

It will print string012345678910.

To get string0, string1 ..... string10, you can use this as YOU suggested:

>>> string = "string"
>>> [string+str(i) for i in range(11)]

edited Apr 03 '22 at 18:07

Peter Mortensen

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answered Aug 21 '13 at 17:45

Anirban Nag 'tintinmj'

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if i input this: `47`, then why do i get this in my string:`u'47'` – TheDoctor Oct 03 '13 at 02:25
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This answer is outdated. Backticks are outdated and have been removed in Python 3. See [this question](http://stackoverflow.com/questions/1673071/what-do-backticks-mean-to-the-python-interpreter-num) for more details. The other answers to this question are better solutions. – Roger Fan Oct 03 '14 at 16:37
Backticks are the equivalent of the `repr()` function, not `str()`. For non-integer values, the `repr()` and `str()` results can differ significantly. – Martijn Pieters Sep 14 '16 at 17:56
SyntaxError: invalid syntax – neoDev Mar 28 '17 at 14:21
@neoDev for which one? – Anirban Nag 'tintinmj' Mar 28 '17 at 15:43
2

in Python3, you can use f-strings like this: string = f'{str}{number}' – Ahmed Rezk Sep 07 '19 at 09:16

YOU · Answer 2 · 2010-05-17T10:00:33.417

277

for i in range (1,10):
    string="string"+str(i)

To get string0, string1 ..... string10, you could do like

>>> ["string"+str(i) for i in range(11)]
['string0', 'string1', 'string2', 'string3', 'string4', 'string5', 'string6', 'string7', 'string8', 'string9', 'string10']

edited May 17 '10 at 10:00

answered May 17 '10 at 07:53

YOU

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It's still worth mentioning that backticks are equivalent to `repr()`, not `str()`. – Bastien Léonard May 17 '10 at 09:06

score 39 · Answer 3 · edited Dec 07 '13 at 21:49

39

for i in range[1,10]: 
  string = "string" + str(i)

The str(i) function converts the integer into a string.

edited Dec 07 '13 at 21:49

Eric Leschinski

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answered May 17 '10 at 07:53

Rizwan Kassim

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score 35 · Answer 4 · answered May 17 '10 at 07:53

35

string = 'string%d' % (i,)

answered May 17 '10 at 07:53

Ignacio Vazquez-Abrams

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you only need to use a list for formatting when you have more than one format specifier, otherwise, it's ugly :) – L̲̳o̲̳̳n̲̳̳g̲̳̳p̲̳o̲̳̳k̲̳̳e̲̳̳ May 17 '10 at 17:50
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That's not a list, that's a tuple. And you also need it if the single item to be formatted is itself a tuple. – Ignacio Vazquez-Abrams May 17 '10 at 20:48

score 22 · Answer 5 · edited Apr 03 '22 at 17:51

22

for i in range(11):
    string = "string{0}".format(i)

You did (range[1,10]):

a TypeError since brackets denote an index (a[3]) or a slice (a[3:5]) of a list,
a SyntaxError since [1,10] is invalid, and
a double off-by-one error since range(1,10) is [1, 2, 3, 4, 5, 6, 7, 8, 9], and you seem to want [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

And string = "string" + i is a TypeError since you can't add an integer to a string (unlike JavaScript).

Look at the documentation for Python's new string formatting method. It is very powerful.

edited Apr 03 '22 at 17:51

Peter Mortensen

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answered May 17 '10 at 08:17

Tim Pietzcker

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(Correction: If you do `range={(1,10): "foo"}`, then `range[1,10]` is in fact a syntactically valid expression.) – Tim Pietzcker Nov 17 '12 at 11:10

score 4 · Answer 6 · edited Apr 03 '22 at 18:01

You can use a generator to do this!

def sequence_generator(limit):
    """ A generator to create strings of pattern -> string1,string2..stringN """
    inc  = 0
    while inc < limit:
        yield 'string' + str(inc)
        inc += 1

# To generate a generator. Notice I have used () instead of []
a_generator  =  (s for s in sequence_generator(10))

# To generate a list
a_list  =  [s for s in sequence_generator(10)]

# To generate a string
a_string =  '['+ ", ".join(s for s in sequence_generator(10)) + ']'

score 1 · Answer 7 · edited Apr 03 '22 at 17:57

1

If we want output like 'string0123456789' then we can use the map function and join method of string.

>>> 'string' + "".join(map(str, xrange(10)))
'string0123456789'

If we want a list of string values then use the list comprehension method.

>>> ['string'+i for i in map(str,xrange(10))]
['string0', 'string1', 'string2', 'string3', 'string4', 'string5', 'string6', 'string7', 'string8', 'string9']

Note:

Use xrange() for Python 2.x.

Use range() for Python 3.x.

edited Apr 03 '22 at 17:57

Peter Mortensen

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answered Jan 05 '15 at 09:10

Vivek Sable

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Perhaps link (non-naked) to documentation for all those functions? (But ***without*** "Edit:", "Update:", or similar - the answer should appear as if it was written today.) – Peter Mortensen Apr 03 '22 at 17:59

score 1 · Answer 8 · edited Apr 03 '22 at 18:06

I did something else.

I wanted to replace a word, in lists of lists, that contained phrases.

I wanted to replace that string / word with a new word that will be a join between string and number, and that number / digit will indicate the position of the phrase / sublist / lists of lists.

That is, I replaced a string with a string and an incremental number that follow it.

myoldlist_1 = [[' myoldword'], [''], ['tttt myoldword'], ['jjjj ddmyoldwordd']]
    No_ofposition = []
    mynewlist_2 = []
    for i in xrange(0, 4, 1):
        mynewlist_2.append([x.replace('myoldword', "%s" % i + "_mynewword") for x in myoldlist_1[i]])
        if len(mynewlist_2[i]) > 0:
            No_ofposition.append(i)

mynewlist_2
No_ofposition

score -6 · Answer 9 · edited Mar 24 '18 at 15:44

-6

Concatenation of a string and integer is simple: just use

abhishek+str(2)

edited Mar 24 '18 at 15:44

Jemshit

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answered Apr 01 '16 at 09:34

Hiro

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If it is so simple, perhaps explain (here or in the answer) why the previous seven answers weren't? E.g., did something change with later versions of Python? – Peter Mortensen Apr 03 '22 at 18:03

Python strings and integer concatenation

9 Answers9

NOTE:

For Python 3

Linked