added chain_extract.py and pdb_chain_extract.py

scripts/my_pdbtools/chain_extract.py

@@ -0,0 +1,24 @@
+#!/usr/bin/python3
+
+#=======================================================================
+# TASK: select specified chains from the pdb & save a cropped PDB with
+# the selected chains. Useful for dimer, etc modelling.
+
+# link for saving each chain as a separate file
+# https://stackoverflow.com/questions/11685716/how-to-extract-chains-from-a-pdb-file
+#=======================================================================
+
+from Bio.PDB import PDBParser, PDBIO, Select
+
+
+# Select() Method to return True for every chain in 'chains'
+class ChainExtract(Select):
+    def __init__(self, chain):
+        self.chain = chain
+    
+    def accept_chain(self, chain):
+        #print(dir(chain))
+        if chain.id in self.chain:
+            return 1
+        else:
+            return 0