String concatenation list comprehension python

I am trying to get this string as a result:

"&markers=97,64&markers=45,84"

From the Python code below:

markers = [[97,64],[45,84]]
result = ["&markers=%s" %x for x in markers]
return result

How do I do this as the below does not give me the actual string?

Gino Mempin

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asked Apr 30, 2013 at 14:21

You need to join your string like this:

markers = [[97,64],[45,84]]
result = ''.join["&markers=%s" % ','.join[map[str, x]] for x in markers]
return result

UPDATE

I didn't initially have the ','.join[map[str, x]] section in there to turn each tuple into strings. This handles varying length tuples, but if you will always have exactly 2 numbers, you might see gatto's comment below.

The explanation of what's going on is that we make a list with one item for each tuple from markers, turning the tuples into comma separated strings which we format into the &markers= string. This list of strings is then joined together separated by an empty string.

perror

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answered Apr 30, 2013 at 14:23

underrununderrun

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In Python 3.6 you could write:

markers = [[97,64],[45,84]]
result = ''.join[f'&markers={pair}' for pair in markers]
return result

Gino Mempin

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answered Oct 16, 2018 at 15:46

PlutoPluto

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While the first answer is doing what's expected, I'd make it a bit more "pythonic" by getting rid of map and nested expressions:

def join[seq, sep=',']:
    return sep.join[str[i] for i in seq]

result = ''.join['&markers=%s' % join[m] for m in markers]

[if that's for urls like it seems, you can also take a look at urllib.urlencode]

answered Apr 30, 2013 at 14:41

berealbereal

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Here's another approach that hopefully makes the intent the most clear by specifying the location of each of your values explicitly:

markers = [[97,64],[45,84]]
print ''.join['&markers=%s,%s' % pair for pair in markers]

answered Apr 30, 2013 at 14:42

hexparrothexparrot

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Try creating an empty string adding to it then removing the last comma

result = ''

for i in a:
    result+='&markers'
    for j in i:
    result += str[j] + ','
result = result[:len[result]-1]

return result

answered Apr 30, 2013 at 14:44

How do you concatenate strings in a list in Python?

You can concatenate a list of strings into a single string with the string method, join[] . Call the join[] method from 'String to insert' and pass [List of strings] . If you use an empty string '' , [List of strings] is simply concatenated, and if you use a comma , , it makes a comma-delimited string.

Is there string comprehension in Python?

List comprehension in Python is an easy and compact syntax for creating a list from a string or another list. It is a very concise way to create a new list by performing an operation on each item in the existing list. List comprehension is considerably faster than processing a list using the for loop.

What are list comprehensions in Python?

A Python list comprehension consists of brackets containing the expression, which is executed for each element along with the for loop to iterate over each element in the Python list. Python List comprehension provides a much more short syntax for creating a new list based on the values of an existing list.

What is dict and list comprehensions are?

In Python, dictionary comprehensions are very similar to list comprehensions – only for dictionaries. They provide an elegant method of creating a dictionary from an iterable or transforming one dictionary into another.

How do you concatenate strings in a list in Python?

Is there string comprehension in Python?

What are list comprehensions in Python?

What is dict and list comprehensions are?

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