How to concatenate a string with every element in a list of strings?

Question

I want to concatenate a string with every element in a given list of strings:

my_variable = 'Blue'
my_list = ['House', 'Paint', 'Cloth']

How do I concatenate my_variable to every element in the my_list such that I have a new list

my_new_list = ['Blue_House', 'Blue_Paint', 'Blue_Cloth']

What have you tried? A simple list comprehension would do this easily. — AChampion, Sep 08 '17 at 20:07
Welcome to SO, this isn't a code writing service, please make an attempt and come back and ask about any problems that you cannot resolve. Please read [ask] and [mcve] — wwii, Sep 08 '17 at 20:12
Possible duplicate of [Appending the same string to a list of strings in Python](https://stackoverflow.com/questions/2050637/appending-the-same-string-to-a-list-of-strings-in-python) — Brad Solomon, Sep 08 '17 at 20:15

Brad Solomon · Answer 1 · 2019-12-09T17:02:49.293

3

Or use a list comprehension:

>>> [my_variable + '_' + e for e in my_list]
['Blue_House', 'Blue_Paint', 'Blue_Cloth']

edited Dec 09 '19 at 17:02

answered Sep 08 '17 at 20:13

Brad Solomon

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score 1 · Answer 2 · answered Sep 09 '17 at 01:11

1

["_".join([my_variable, i]) for i in my_list]
# ['Blue_House', 'Blue_Paint', 'Blue_Cloth']

answered Sep 09 '17 at 01:11

pylang

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MattWBP · Answer 3 · 2017-09-08T20:14:45.460

0

Create a new list and iterate through your original list, appending the original list's entry to the new list with 'Blue_' added to the front with a simple +

my_variable = 'Blue'
my_list = ['House', 'Paint', 'Cloth']

new_list = []
for entry in my_list:
    new_list.append(my_variable + "_" + str(entry))

print new_list
>>>>['Blue_House', 'Blue_Paint', 'Blue_Cloth']

edited Sep 08 '17 at 20:14

answered Sep 08 '17 at 20:08

MattWBP

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I tried but I get: TypeError: cannot concatenate 'str' and 'list' objects – JungleDiff Sep 08 '17 at 20:12
It sounds like you're not properly iterating through your list (which contains strings) but are trying to concatenate the list itself with the string. Try running the exact code I sent, I've updated it to work with your example input. – MattWBP Sep 08 '17 at 20:18

score -1 · Answer 4 · answered Sep 09 '17 at 08:52

my_variable1 = 'Blue'
my_variable2 = 'Red'
my_variable3 = 'Black'
my_list = ['House', 'Paint', 'Cloth']

def mergetwo(a, b, s):
    return s.join((a,b))

def prefix(item, pre):
    return lambda sep: mergetwo(pre,item,sep)

def suffix(item, suf):
    return prefix(suf, item)

def mergewith(alist):
    return lambda position: lambda sep: lambda var: list(map(lambda item: position(item, var)(sep), alist))

def addprefix_underscore_mylist(var):
    return mergewith(my_list)(prefix)('_')(var)

def addsuffix_underscore_mylist(var):
    return mergewith(my_list)(suffix)('_')(var)

print(addprefix_underscore_mylist(my_variable1))
print(addprefix_underscore_mylist(my_variable2))
print(addprefix_underscore_mylist(my_variable3))

print(addsuffix_underscore_mylist(my_variable1))
print(addsuffix_underscore_mylist(my_variable2))
print(addsuffix_underscore_mylist(my_variable3))

How to concatenate a string with every element in a list of strings?

4 Answers4