Add acispy/header.py to read/write/copy FITS header keywords

1 files changed, 77 insertions, 0 deletions

diff --git a/acispy/header.py b/acispy/header.py
new file mode 100644
index 0000000..0614cd6
--- /dev/null
+++ b/acispy/header.py
@@ -0,0 +1,77 @@
+# Copyright (c) 2017 Weitian LI <liweitianux@live.com>
+# MIT license
+
+"""
+Manipulate the FITS header keywords using CIAO tools
+``dmkeypar`` and ``dmhedit``.
+"""
+
+import subprocess
+
+
+def read_keyword(infile, keyword):
+    """
+    Read the specified header keyword, and return a dictionary
+    with its value, unit, data type, and comment.
+    """
+    DATATYPES = {
+        "real": float,
+        "integer": int,
+        "boolean": bool,
+        "string": str
+    }
+    subprocess.check_call(["punlearn", "dmkeypar"])
+    subprocess.check_call([
+        "dmkeypar", "infile=%s" % infile, "keyword=%s" % keyword
+    ])
+    datatype = subprocess.check_output([
+        "pget", "dmkeypar", "datatype"
+    ]).decode("utf-8").strip()
+    value = subprocess.check_output([
+        "pget", "dmkeypar", "value"
+    ]).decode("utf-8").strip()
+    value = DATATYPES[datatype](value)
+    unit = subprocess.check_output([
+        "pget", "dmkeypar", "unit"
+    ]).decode("utf-8").strip()
+    comment = subprocess.check_output([
+        "pget", "dmkeypar", "comment"
+    ]).decode("utf-8").strip()
+    return {"value": value, "datatype": datatype,
+            "unit": unit, "comment": comment}
+
+
+def write_keyword(infile, keyword, value, datatype=None,
+                  unit=None, comment=None):
+    """
+    Write the specified keyword to the file header.
+    """
+    DATATYPES = {
+        "real": "double",
+        "integer": "long",
+        "boolean": "boolean",
+        "string": "string"
+    }
+    subprocess.check_call(["punlearn", "dmhedit"])
+    cmd = [
+        "dmhedit", "infile=%s" % infile, "filelist=none",
+        "operation=add", "key=%s" % keyword, "value=%s" % value
+    ]
+    if datatype:
+        cmd += ["datatype=%s" % DATATYPES[datatype]]
+    if unit:
+        cmd += ["unit=%s" % unit]
+    if comment:
+        cmd += ["comment=%s" % comment]
+    subprocess.check_call(cmd)
+
+
+def copy_keyword(infile1, infile2, keyword):
+    """
+    Copy the specified keyword(s) from infile1 to infile2.
+    """
+    if not isinstance(keyword, list):
+        keyword = [keyword]
+    for kw in keyword:
+        data = read_keyword(infile1, kw)
+        write_keyword(infile2, kw, **data)