string concatenation

[Peter Otten]

selwyn wrote:

> you can += strings, but you need to create the variable first:
> 
> i.e.
> for name in contextForm.keys():
>      context = ''
>      context += "Input: " + name + " value: " + contextForm[name].value
> + "<BR>"

I guess the OP wants to collect data over the loop, i. e

context = ""
for name in contextForm.keys():
    context += "Input: " + name + " value: " + contextForm[name].value
 
> concatenating a string like this is supposed to be substantially slower
> than using ''.join(sequence), where you can replace the blank string
> with the separator of your choice.
> 
> using your example:
> 
> for name in contextForm.keys():
>      sequence = ["Input: ",name, " value: ", contextForm[name].value,
> "<BR>"]
>      context = ' '.join(sequence)

The faster idiom will then become

sequence = []
for name in contextForm.keys():
    sequence += ["Input: ", name, " value: ", contextForm[name].value,
        "<BR>"]
context = "".join(sequence)
 
Peter