ch05: new chapter

05-record-like/struct/metro_read.py

@@ -0,0 +1,15 @@
+from struct import iter_unpack
+
+FORMAT = 'i12s2sf'                             # <1>
+
+def text(field: bytes) -> str:                 # <2>
+    octets = field.split(b'\0', 1)[0]          # <3>
+    return octets.decode('cp437')              # <4>
+
+with open('metro_areas.bin', 'rb') as fp:      # <5>
+    data = fp.read()
+
+for fields in iter_unpack(FORMAT, data):       # <6>
+    year, name, country, pop = fields
+    place = text(name) + ', ' + text(country)  # <7>
+    print(f'{year}\t{place}\t{pop:,.0f}')