2 new tips

index.md

@@ -212,6 +212,7 @@ This file gets generated by [this script](index.py).
 
 - [Itertools.count](notes/20220906094357.md)
 - [Pathlib list files in directory](notes/20220904164101.md)
+- [Slicing generators](notes/20240711112100.md)
 - [Split a sequence into pairs](notes/20231216210001.md)
 
 ## Git
@@ -332,6 +333,10 @@ This file gets generated by [this script](index.py).
 - [Pathlib list files in directory](notes/20220904164101.md)
 - [Read / write files the modern way](notes/20221202131250.md)
 
+## Pdf
+
+- [Merge pdf files](notes/20240711112142.md)
+
 ## Performance
 
 - [More performant string building](notes/20231218133029.md)

notes/20240711112100.md

@@ -0,0 +1,35 @@
+# slicing generators
+
+Ever wondered how to slice a #Python generator?
+
+You can use `itertools.islice()`:
+
+```
+>>> def gen():
+...     yield from range(1, 11)
+...
+>>> g = gen()
+
+>>> g[:2]
+Traceback (most recent call last):
+  File "<stdin>", line 1, in <module>
+TypeError: 'generator' object is not subscriptable
+
+>>> from itertools import islice
+>>> my_slice = islice(g, 2)
+>>> my_slice
+<itertools.islice object at 0x7fb2ab084540>
+>>> list(my_slice)
+[1, 2]
+>>> [i for i in g]
+[3, 4, 5, 6, 7, 8, 9, 10]
+
+# another example of generator exhaustion:
+>>> g = gen()
+>>> ', '.join(str(i) for i in g)
+'1, 2, 3, 4, 5, 6, 7, 8, 9, 10'
+>>> ', '.join(str(i) for i in g)
+''
+```
+
+#generators

notes/20240711112142.md

@@ -0,0 +1,21 @@
+# merge PDF files
+
+TIL how to merge PDF files in Python -> the `pypdf` library makes this really easy:
+
+```
+from itertools import islice
+from pathlib import Path
+
+from pypdf import PdfWriter
+
+with PdfWriter() as merger:
+    files = (Path.home() / "code" / "articles" / "outputs").glob('*.pdf')
+    for file in islice(files, 3):
+        merger.append(file)
+    merger.write("output.pdf")
+```
+
+Source project where I found this: https://github.com/ahmedlemine/pdf-merger
+
+#pdf
+