How to export data to a plain text file?

Question

I am preparing data used by a command line program. It requires data in a simpliest possible format:

value_x1 value_y1
value_x2 value_y2
...    
value_xN value_yN

For now I always need to use Python to process a datafile created in Mathematica that format, because Mathematica always adds quotes " or multiple blank spaces or tabs. How can I create a file in a format:

<value_x1><single_space_sign><value_y1><end_of_line_sign>
<value_x2><single_space_sign><value_y2><end_of_line_sign>
...    
<value_xN><single_space_sign><value_yN><end_of_line_sign>

OpenWrite[], Write[], Export[,"Table"] etc. produce files with additional characters, and therefore are useless without processing in Python.

Edit: What if I needed to create a file in a format:

<value_x1><single_space_sign><some string character><value_y1><end_of_line_sign>
<value_x2><single_space_sign><some string character><value_y2><end_of_line_sign>
...    
<value_xN><single_space_sign><some string character><value_yN><end_of_line_sign>

Edit 2: Proposed answer:

dat = Table[{i, Sin[i]}, {i, 4}] // N;
Export["test.dat", dat]

produces file containing following data:

{1., 0.8414709848078965}
{2., 0.9092974268256817}
{3., 0.1411200080598672}
{4., -0.7568024953079282}

Which is useless.

Answer 1

dat = Table[{i, Sin[i], Cos[i], Tan[i]}, {i, 4}] // N;

Export["test.txt", dat, "Table",  "FieldSeparators" -> " "]

FilePrint["test.txt"]

1. 0.8414709848078965 0.5403023058681397 1.5574077246549023
2. 0.9092974268256817 -0.4161468365471424 -2.185039863261519
3. 0.1411200080598672 -0.9899924966004454 -0.1425465430742778
4. -0.7568024953079282 -0.6536436208636119 1.1578212823495777

Nothing new here. It's all in the documentation.

Answer 2

Try

dat = Table[{i, Sin[i]}, {i, 4}] // N;
Export["test.dat", dat]

So that

 FilePrint["test.dat"]

returns

(* 1. 0.8414709848078965 2. 0.9092974268256817 3. 0.1411200080598672 4. -0.7568024953079282 *)

Answer 3

I don't know if this may be the issue, but specifying "FieldSeparators" to a space causes multi-word strings to be quoted:

 ExportString[{{1, 1}, {"dog", "and cat"}}, "Table",  "FieldSeparators" -> " "]

1 1

dog "and cat"

Fix with TextDelimiters

 ExportString[{{1, 1}, {"dog", "and cat"}}, "Table", 
     "FieldSeparators" -> " ", "TextDelimiters" -> ""]

1 1

dog and cat

Obviously you now can't simply read it back in as a table recovering the original strings.

(verifed for export to files under Windows using either a ".dat" extension, or the "Table" argument)