Recursive insertion of a line

[Francesco Pietra]

New to the list and just beginning with Python (Linux B console). Urgent
problem before I can correctly program:

How to insert "TER" records recursively, i.e. some thousand fold,  in a file
like in the following example? "H2 WAT" is the only constant characteristic of
the line after which to insert "TER"; that distinguishes also for lines for
other atoms. Just to illustrate what I want to do - for those unfamiliar with
this type of file - a three-line set between two "TER" defines a water
molecule, with a set of xyz coordinates for each atom.

TER
ATOM  27394  O   WAT  3966      17.713  13.305  27.101  1.00  0.00      W20  O
ATOM  27395  H1  WAT  3966      17.814  13.945  26.397  1.00  0.00      W20  H
ATOM  27396  H2  WAT  3966      16.776  13.297  27.297  1.00  0.00      W20  H
TER
ATOM  27397  O   WAT  4144       0.648   8.291  27.112  1.00  0.00      W20  O
ATOM  27398  H1  WAT  4144       0.344   8.314  26.205  1.00  0.00      W20  H
ATOM  27399  H2  WAT  4144       1.278   7.571  27.144  1.00  0.00      W20  H
TER
ATOM  27400  O   WAT  4178      20.289   4.598  26.491  1.00  0.00      W20  O
ATOM  27401  H1  WAT  4178      19.714   3.835  26.423  1.00  0.00      W20  H
ATOM  27402  H2  WAT  4178      21.173   4.237  26.554  1.00  0.00      W20  H
TER

Thanks
francesco pietra



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