Différences

Ci-dessous, les différences entre deux révisions de la page.

--- tech:python-draft [2025/04/15 17:15] – Jean-Baptiste
+++ tech:python-draft [2025/05/26 18:56] (Version actuelle) – Jean-Baptiste
@@ Ligne 1: / Ligne 1: @@
+<!DOCTYPE markdown>
+{{tag>Code Python}}
+# Draft Python3
+## List comprehensions and generator expressions
+ (short form: “listcomps” and “genexps”)
+~~~python
+line_list = ['  line 1\n', 'line 2  \n', ' \n', '']
+# Generator expression -- returns iterator
+stripped_iter = (line.strip() for line in line_list)
+# List comprehension -- returns list
+stripped_list = [line.strip() for line in line_list]
+stripped_list = [line.strip() for line in line_list if line != ""]
+~~~
+### Autres
+~~~python
+def inc(f, id):
+    """ Exemple : inc(lambda x : x+1, 0) """
+    try :
+        global counter
+        counter = f(counter)
+    except NameError:
+        counter = 0
+    return counter
+~~~
+------------
+http://mgautier.fr/blog/Astuce/changer-lenvironnement-bash-avec-python.html
+------------
+## List unique remove duplicate
+Source :
+http://stackoverflow.com/questions/89178/in-python-what-is-the-fastest-algorithm-for-removing-duplicates-from-a-list-so
+~~~python
+def unique(items):
+    found = set([])
+    keep = []
+    for item in items:
+        if item not in found:
+            found.add(item)
+            keep.append(item)
+    return keep
+~~~
+------------
+## How do you split a list into evenly sized chunks in Python?
+Source : http://stackoverflow.com/questions/312443/how-do-you-split-a-list-into-evenly-sized-chunks-in-python
+~~~python
+def chunks(l, n):
+    n = max(1, n)
+    return [l[i:i + n] for i in range(0, len(l), n)]
+~~~
+-------------
+## Determine if variable is defined in Python
+http://stackoverflow.com/questions/1592565/determine-if-variable-is-defined-in-python
+~~~python
+try:
+  thevariable
+except NameError:
+  print "well, it WASN'T defined after all!"
+else:
+  print "sure, it was defined."
+~~~
+I think it's better to avoid the situation. It's cleaner and clearer to write:
+~~~python
+a = None
+if condition:
+    a = 42
+~~~
+------------
+## Getting file size in Python
+http://stackoverflow.com/questions/6591931/getting-file-size-in-python
+~~~python
+def get_Size(file):
+    file.seek(0,2) # move the cursor to the end of the file
+    size = file.tell()
+    return size
+~~~
+Exemple :
+~~~python
+with open('plop.bin','rb') as file:
+    size=get_Size(file)
+with open('plop.bin','rb') as file:
+    #size=get_Size(file)
+    for i in range(size):
+        un, deux = read_hexafile()
+        msg.append(un)
+        msg.append(deux)
+~~~
+''/dev/null''
+~~~python
+fnull = open(os.devnull, 'w')
+~~~
+-----------------
+## Message d'erreur
+How to print to stderr in Python?
+http://stackoverflow.com/questions/5574702/how-to-print-to-stderr-in-python
+~~~python
+def warning(*objs):
+    print(*objs, file=sys.stderr)
+~~~
+## Conversion hexa
+~~~python
+import numpy as np
+carac=re.sub('^','0x',carac)
+carac= int(carac, 16)
+print(carac)
+file.write(np.byte(carac))
+with open('plop.bin', 'bw') as file:
+        file.write(b'\x50\x40\x73')
+hex(11) # '0xb'
+a = int('0x100', 16)
+print(a)   #256
+print('%x' % a) #100
+import binascii
+binascii.unhexlify('7061756c')  # b'paul'
+"{0:8b}".format(int("a",16))    # '    1010'
+~~~
+http://stackoverflow.com/questions/16843108/how-to-read-a-hex-file-into-numpy-array
+~~~python
+with open(myfile) as f:
+    iv = binascii.unhexlify(f.readline().strip())
+    key = binascii.unhexlify(f.readline().strip())
+    count = int(f.readline())
+    a = np.fromiter((binascii.unhexlify(line.strip()) for line in f), dtype='|S16')
+~~~
+~~~python
+hashlib.sha512('Bonjour'.encode('utf-8')).hexdigest()
+hex(int.from_bytes('Bonjour'.encode('utf-8'), 'big'))
+~~~
+--------
+Créer un Dictionnaire à partir de deux listes (l'une clef, l'autre valeur)
+~~~python
+clef = ['a', 'b', 'c']
+valeur = [1, 2, 3]
+dictionnaire=dict(zip(clef, valeur))
+~~~
+## Test
+Voir :
+* nox
+* unittest
+## Exception
+http://stackoverflow.com/questions/16138232/is-it-a-good-practice-to-use-try-except-else-in-python
+~~~python
+try:
+    s
+except NameError:
+    pass
+else: # If no exception occured, do :
+    s.user.logout()
+~~~
+## Temps / time
+Voir :
+* timeit
+~~~python
+start = time.time()
+UnifiedJob.objects.filter(id=1096679).update(status='canceled')
+end = time.time()
+print(end - start)
+~~~
+## Strings
+https://zerokspot.com/weblog/2015/12/31/new-string-formatting-in-python/
+## Debug
+Source : https://www.geekarea.fr/wordpress/?p=763
+Level 1
+~~~python
+f = open('/tmp/debug','a')
+f.write(variable + '\n')
+f.close()
+~~~
+Level 2
+~~~python
+from pprint import pprint
+pprint(variable.__class__.__name__, f)
+pprint(dir(variable), f)
+pprint(vars(variable), f)
+~~~
+Level 3 (sur une exception)
+~~~python
+import traceback
+f.write(str(traceback.format_exc()))
+~~~
+## map reduce filter
+Voir :
+* [[notes_python_multithreading|Alternatives Multi threads à map]]
+## Aures
+A noter que sur RedHat 8 le chemin vers python est ''/usr/libexec/platform-python''