python - How to append all the loop elements in single line while using string Template? -

i have tried make template example.py using string template substitute each loop elements in $i ["ca:"+$i+':'+" "]. partially works substituting last element.

but, want append values in single line format .

for example:

what current script doing follows:

for in range(1,4):     #it takes each "i" elements , substituting last element     str='''s=selection( self.atoms["ca:"+$i+':'+" "].select_sphere(10) ) 

what getting follows:

    s=selection( self.atoms["ca:"+3+':'+" "].select_sphere(10) ) 

what, expecting follows:

    s=selection ( self.atoms["ca:"+1+':'+" "].select_sphere(10),self.atoms["ca:"+2+':'+" "].select_sphere(10),self.atoms["ca:"+3+':'+" "].select_sphere(10) ) 

my script:

import os string import template in range(1,4):      str='''     s=selection( self.atoms["ca:"+$i+':'+" "].select_sphere(10) )     '''     str=template(str)     file = open(os.getcwd() + '/' + 'example.py', 'w')     file.write(str.substitute(i=i))     file.close() 

i use 2 scripts desired output:

import os string import template a=[] in range(1,4):      a.append(''.join("self.atoms["+ "'ca:' "+str(i)+""':'+" "+"]"+".select_sphere(10)"))  str='''s=selection( $a ).by_residue()''' str=template(str) file = open(os.getcwd() + '/' + 'example.py', 'w') file.write(str.substitute(a=a))  open('example.py', 'w') outfile:      selection_template = '''self.atoms["ca:"+{}+':'+" "].select_sphere(10)'''      selections = [selection_template.format(i) in range(1, 4)]      outfile.write('s = selection({})\n'.format(', '.join(selections))) 

one problem code, because opens output file mode 'w', overwrites file on each iteration of loop. why see last 1 in file.

also wouldn't use string.template perform these substitutions. use str.format(). generate list of selections , use str.join() produce final string:

with open('example.py', 'w') outfile:     selection_template = 'self.atoms["ca:"+{}+":"+" "].select_sphere(10)'     selections = [selection_template.format(i) in range(1, 4)]     outfile.write('s = selection({})\n'.format(', '.join(selections))) 

here selection_template uses {} placeholder variable substitution , list comprehension used construct selection strings. these selection strings joined using string ', ' separator , resulting string inserted call selection(), again using str.format().