Merge pull request #2416 from megies/multipage_pdf_with_statement

Multipage pdf with statement

examples/pylab_examples/multipage_pdf.py

@@ -2,42 +2,39 @@
 
 import datetime
 import numpy as np
-import matplotlib
 from matplotlib.backends.backend_pdf import PdfPages
-from pylab import *
+import matplotlib.pyplot as plt
 
 # Create the PdfPages object to which we will save the pages:
-pdf = PdfPages('multipage_pdf.pdf')
+# The with statement makes sure that the PdfPages object is closed properly at
+# the end of the block, even if an Exception occurs.
+with PdfPages('multipage_pdf.pdf') as pdf:
+    plt.figure(figsize=(3, 3))
+    plt.plot(range(7), [3, 1, 4, 1, 5, 9, 2], 'r-o')
+    plt.title('Page One')
+    pdf.savefig()  # saves the current figure into a pdf page
+    plt.close()
 
-figure(figsize=(3,3))
-plot(range(7), [3,1,4,1,5,9,2], 'r-o')
-title('Page One')
-savefig(pdf, format='pdf') # note the format='pdf' argument!
-close()
+    plt.rc('text', usetex=True)
+    plt.figure(figsize=(8, 6))
+    x = np.arange(0, 5, 0.1)
+    plt.plot(x, np.sin(x), 'b-')
+    plt.title('Page Two')
+    pdf.savefig()
+    plt.close()
 
-rc('text', usetex=True)
-figure(figsize=(8,6))
-x = np.arange(0,5,0.1)
-plot(x, np.sin(x), 'b-')
-title('Page Two')
-pdf.savefig() # here's another way - or you could do pdf.savefig(1)
-close()
+    plt.rc('text', usetex=False)
+    fig = plt.figure(figsize=(4, 5))
+    plt.plot(x, x*x, 'ko')
+    plt.title('Page Three')
+    pdf.savefig(fig)  # or you can pass a Figure object to pdf.savefig
+    plt.close()
 
-rc('text', usetex=False)
-fig=figure(figsize=(4,5))
-plot(x, x*x, 'ko')
-title('Page Three')
-pdf.savefig(fig) # or you can pass a Figure object to pdf.savefig
-close()
-
-# We can also set the file's metadata via the PdfPages object:
-d = pdf.infodict()
-d['Title'] = 'Multipage PDF Example'
-d['Author'] = u'Jouni K. Sepp\xe4nen'
-d['Subject'] = 'How to create a multipage pdf file and set its metadata'
-d['Keywords'] = 'PdfPages multipage keywords author title subject'
-d['CreationDate'] = datetime.datetime(2009,11,13)
-d['ModDate'] = datetime.datetime.today()
-
-# Remember to close the object - otherwise the file will not be usable
-pdf.close()
+    # We can also set the file's metadata via the PdfPages object:
+    d = pdf.infodict()
+    d['Title'] = 'Multipage PDF Example'
+    d['Author'] = u'Jouni K. Sepp\xe4nen'
+    d['Subject'] = 'How to create a multipage pdf file and set its metadata'
+    d['Keywords'] = 'PdfPages multipage keywords author title subject'
+    d['CreationDate'] = datetime.datetime(2009, 11, 13)
+    d['ModDate'] = datetime.datetime.today()

lib/matplotlib/backends/backend_pdf.py

@@ -2248,15 +2248,12 @@ class PdfPages(object):
     Use like this::
 
         # Initialize:
-        pp = PdfPages('foo.pdf')
+        with PdfPages('foo.pdf') as pdf:
 
-        # As many times as you like, create a figure fig, then either:
-        fig.savefig(pp, format='pdf') # note the format argument!
-        # or:
-        pp.savefig(fig)
-
-        # Once you are done, remember to close the object:
-        pp.close()
+            # As many times as you like, create a figure fig and save it:
+            # When no figure is specified the current figure is saved
+            pdf.savefig(fig)
+            pdf.savefig()
 
     (In reality PdfPages is a thin wrapper around PdfFile, in order to
     avoid confusion when using savefig and forgetting the format
@@ -2272,6 +2269,12 @@ def __init__(self, filename):
         """
         self._file = PdfFile(filename)
 
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self.close()
+
     def close(self):
         """
         Finalize this object, making the underlying file a complete