Python
Main page for all things Python. Other pages cover specific topics, such as:
Boolean unravelling
and
unravelling the and boolean operator. The operation can be rewritten as the
function u_and:
def u_and(a, b):
result = a
if a:
result = b
return result
For instance:
a = True ; b = None
print(a and b, u_and(a, b))
a = True ; b = True
print(a and b, u_and(a, b))
a = False ; b = True
print(a and b, u_and(a, b))
None None
True True
False False
or
On the other hand, or cand be unravelled as:
def u_or(a, b):
result = a
if not a:
result = b
return result
As an example:
a = True ; b = None
print(a or b, u_or(a, b))
a = True ; b = True
print(a or b, u_or(a, b))
a = False ; b = True
print(a or b, u_or(a, b))
True True
True True
True True
The many faces of print
Concatenating arguments
var1 = "Foo"
var2 = "Bar"
print("I am ", var1, " not ", var2)
I am Foo not Bar
var1 = "Foo"
var2 = "Bar"
print("I am ", var1, " not ", var2)
I am Foo not Bar
It is also possible to use separators by using the sep argument:
var1 = "Foo"
var2 = "Bar"
print("I am", var1, "not", var2, sep="!")
I am!Foo!not!Bar
String termination
The end argument allows to specify the suffix of the whole string.
print("This is on radio", end=" (over)")
This is on radio (over)
Filesystem operations
Get home directory
For Python +3.5:
from pathlib import Path
home = str(Path.home())
List files recursively
For Python +3.5, use glob:
import glob
# root_dir with trailing slash (i.e. /root/dir/)
root_dir = "./tmp"
for filename in glob.iglob(root_dir + '**/*.md', recursive=True):
print(filename)
Collections
Sort an object list by attribute
Assuming a list a with instances of Foo, such that
import random
from dataclasses import dataclass
@dataclass
class Foo:
bar: str
baz: int
a = [Foo(bar=f"foo-{i}", baz=random.randint(0, 100)) for i in range(50)]
a[1:5]
[Foo(bar='foo-1', baz=3),
Foo(bar='foo-2', baz=30),
Foo(bar='foo-3', baz=56),
Foo(bar='foo-4', baz=34)]
To return a new collection:
a_sorted = sorted(a, key=lambda x: x.baz, reverse=False)
a_sorted[1:5]
[Foo(bar='foo-1', baz=3),
Foo(bar='foo-28', baz=3),
Foo(bar='foo-41', baz=5),
Foo(bar='foo-15', baz=6)]
To sort in place using attribute bar:
a.sort(key=lambda x: x.baz, reverse=True)
a[1:5]
[Foo(bar='foo-40', baz=91),
Foo(bar='foo-18', baz=87),
Foo(bar='foo-37', baz=86),
Foo(bar='foo-43', baz=86)]