1.10. Modules¶
# Afficher la table des matières
from jyquickhelper import add_notebook_menu
add_notebook_menu()
Un module contient un ensemble de fonctions et commandes
Python dispose d’une bibliothèque de base quand il est initialisé. Et selon nos besoins ces bibliothèques vont être chargées.
Pour utiliser un module, il faut l’importer.
Nous avons deux types de modules : ceux disponibles sur Internet (programmés par d’autres) et ceux que l’on programme soi-même.
Pour les modules disponibles, les bibliothèques souvent utiles pour faire un programme python scientifique, nous avons : import os import sys import numpy as np import math
import random import csv import scipy import matplotlib . pylab as plt
1.10.1. Syntaxe d’importation¶
Syntaxe 1 : importer le module sous son nom
import math
# on peut utiliser math.sin, math.sqrt...
Syntaxe 2 : importer le module sous un nom différent - permet d’abréger le nom des modules
import math as m
# on utilise m.sin, m.sqrt...
Syntaxe 3 : importer seulement certaines définitions
from math import sqrt
# on peut utiliser uniquement sqrt (les autres fonctions math.sin..., ne sont pas reconnu)
On peut utiliser help pour obtenir de l’aide sur les modules importés.
help(math)
Help on module math:
NAME
math
MODULE REFERENCE
https://docs.python.org/3.8/library/math
The following documentation is automatically generated from the Python
source files. It may be incomplete, incorrect or include features that
are considered implementation detail and may vary between Python
implementations. When in doubt, consult the module reference at the
location listed above.
DESCRIPTION
This module provides access to the mathematical functions
defined by the C standard.
FUNCTIONS
acos(x, /)
Return the arc cosine (measured in radians) of x.
acosh(x, /)
Return the inverse hyperbolic cosine of x.
asin(x, /)
Return the arc sine (measured in radians) of x.
asinh(x, /)
Return the inverse hyperbolic sine of x.
atan(x, /)
Return the arc tangent (measured in radians) of x.
atan2(y, x, /)
Return the arc tangent (measured in radians) of y/x.
Unlike atan(y/x), the signs of both x and y are considered.
atanh(x, /)
Return the inverse hyperbolic tangent of x.
ceil(x, /)
Return the ceiling of x as an Integral.
This is the smallest integer >= x.
comb(n, k, /)
Number of ways to choose k items from n items without repetition and without order.
Evaluates to n! / (k! * (n - k)!) when k <= n and evaluates
to zero when k > n.
Also called the binomial coefficient because it is equivalent
to the coefficient of k-th term in polynomial expansion of the
expression (1 + x)**n.
Raises TypeError if either of the arguments are not integers.
Raises ValueError if either of the arguments are negative.
copysign(x, y, /)
Return a float with the magnitude (absolute value) of x but the sign of y.
On platforms that support signed zeros, copysign(1.0, -0.0)
returns -1.0.
cos(x, /)
Return the cosine of x (measured in radians).
cosh(x, /)
Return the hyperbolic cosine of x.
degrees(x, /)
Convert angle x from radians to degrees.
dist(p, q, /)
Return the Euclidean distance between two points p and q.
The points should be specified as sequences (or iterables) of
coordinates. Both inputs must have the same dimension.
Roughly equivalent to:
sqrt(sum((px - qx) ** 2.0 for px, qx in zip(p, q)))
erf(x, /)
Error function at x.
erfc(x, /)
Complementary error function at x.
exp(x, /)
Return e raised to the power of x.
expm1(x, /)
Return exp(x)-1.
This function avoids the loss of precision involved in the direct evaluation of exp(x)-1 for small x.
fabs(x, /)
Return the absolute value of the float x.
factorial(x, /)
Find x!.
Raise a ValueError if x is negative or non-integral.
floor(x, /)
Return the floor of x as an Integral.
This is the largest integer <= x.
fmod(x, y, /)
Return fmod(x, y), according to platform C.
x % y may differ.
frexp(x, /)
Return the mantissa and exponent of x, as pair (m, e).
m is a float and e is an int, such that x = m * 2.**e.
If x is 0, m and e are both 0. Else 0.5 <= abs(m) < 1.0.
fsum(seq, /)
Return an accurate floating point sum of values in the iterable seq.
Assumes IEEE-754 floating point arithmetic.
gamma(x, /)
Gamma function at x.
gcd(x, y, /)
greatest common divisor of x and y
hypot(...)
hypot(*coordinates) -> value
Multidimensional Euclidean distance from the origin to a point.
Roughly equivalent to:
sqrt(sum(x**2 for x in coordinates))
For a two dimensional point (x, y), gives the hypotenuse
using the Pythagorean theorem: sqrt(x*x + y*y).
For example, the hypotenuse of a 3/4/5 right triangle is:
>>> hypot(3.0, 4.0)
5.0
isclose(a, b, *, rel_tol=1e-09, abs_tol=0.0)
Determine whether two floating point numbers are close in value.
rel_tol
maximum difference for being considered "close", relative to the
magnitude of the input values
abs_tol
maximum difference for being considered "close", regardless of the
magnitude of the input values
Return True if a is close in value to b, and False otherwise.
For the values to be considered close, the difference between them
must be smaller than at least one of the tolerances.
-inf, inf and NaN behave similarly to the IEEE 754 Standard. That
is, NaN is not close to anything, even itself. inf and -inf are
only close to themselves.
isfinite(x, /)
Return True if x is neither an infinity nor a NaN, and False otherwise.
isinf(x, /)
Return True if x is a positive or negative infinity, and False otherwise.
isnan(x, /)
Return True if x is a NaN (not a number), and False otherwise.
isqrt(n, /)
Return the integer part of the square root of the input.
ldexp(x, i, /)
Return x * (2**i).
This is essentially the inverse of frexp().
lgamma(x, /)
Natural logarithm of absolute value of Gamma function at x.
log(...)
log(x, [base=math.e])
Return the logarithm of x to the given base.
If the base not specified, returns the natural logarithm (base e) of x.
log10(x, /)
Return the base 10 logarithm of x.
log1p(x, /)
Return the natural logarithm of 1+x (base e).
The result is computed in a way which is accurate for x near zero.
log2(x, /)
Return the base 2 logarithm of x.
modf(x, /)
Return the fractional and integer parts of x.
Both results carry the sign of x and are floats.
perm(n, k=None, /)
Number of ways to choose k items from n items without repetition and with order.
Evaluates to n! / (n - k)! when k <= n and evaluates
to zero when k > n.
If k is not specified or is None, then k defaults to n
and the function returns n!.
Raises TypeError if either of the arguments are not integers.
Raises ValueError if either of the arguments are negative.
pow(x, y, /)
Return x**y (x to the power of y).
prod(iterable, /, *, start=1)
Calculate the product of all the elements in the input iterable.
The default start value for the product is 1.
When the iterable is empty, return the start value. This function is
intended specifically for use with numeric values and may reject
non-numeric types.
radians(x, /)
Convert angle x from degrees to radians.
remainder(x, y, /)
Difference between x and the closest integer multiple of y.
Return x - n*y where n*y is the closest integer multiple of y.
In the case where x is exactly halfway between two multiples of
y, the nearest even value of n is used. The result is always exact.
sin(x, /)
Return the sine of x (measured in radians).
sinh(x, /)
Return the hyperbolic sine of x.
sqrt(x, /)
Return the square root of x.
tan(x, /)
Return the tangent of x (measured in radians).
tanh(x, /)
Return the hyperbolic tangent of x.
trunc(x, /)
Truncates the Real x to the nearest Integral toward 0.
Uses the __trunc__ magic method.
DATA
e = 2.718281828459045
inf = inf
nan = nan
pi = 3.141592653589793
tau = 6.283185307179586
FILE
/opt/anaconda3/lib/python3.8/lib-dynload/math.cpython-38-darwin.so
ou, si on veut connaître en seul coup d’oeil toutes les méthodes ou variables associées à un module (ou objet), on peut utiliser la commande dir
print(dir(math))
['__doc__', '__file__', '__loader__', '__name__', '__package__', '__spec__', 'acos', 'acosh', 'asin', 'asinh', 'atan', 'atan2', 'atanh', 'ceil', 'comb', 'copysign', 'cos', 'cosh', 'degrees', 'dist', 'e', 'erf', 'erfc', 'exp', 'expm1', 'fabs', 'factorial', 'floor', 'fmod', 'frexp', 'fsum', 'gamma', 'gcd', 'hypot', 'inf', 'isclose', 'isfinite', 'isinf', 'isnan', 'isqrt', 'ldexp', 'lgamma', 'log', 'log10', 'log1p', 'log2', 'modf', 'nan', 'perm', 'pi', 'pow', 'prod', 'radians', 'remainder', 'sin', 'sinh', 'sqrt', 'tan', 'tanh', 'tau', 'trunc']
1.10.1.1. Modules courants¶
Il existe une série de modules que vous serez probablement amenés à utiliser si vous programmez en Python. En voici une liste non exhaustive. Pour la liste complète, reportez-vous àla page des modules sur le site de Python :
*math : fonctions et constantes mathématiques de base (sin, cos, exp, pi…).
*sys : passage d’arguments, gestion de l’entrée/sortie standard…
*os : dialogue avec le système d’exploitation (e.g. permet de sortir de Python, lancer une commande en {\it shell}, puis de revenir à Python).
*random : génération de nombres aléatoires.
*time : permet d’accéder à l’heure de l’ordinateur et aux fonctions gérant le temps.
*calendar : fonctions de calendrier.
*profile : permet d’évaluer le temps d’exécution de chaque fonction dans un programme ({\it profiling} en anglais).
*urllib2 : permet de récupérer des données sur internet depuis python.
*Tkinter : interface python avec Tk (permet de créer des objets graphiques; nécessite d’installer Tk.
*re : gestion des expressions régulières.
Je vous conseille vivement d’aller surfer sur les pages de ces modules pour découvrir toutes leurs potentialités.
1.10.2. Création de vos propres modules¶
Vous pouvez également définir vos propres modules.
Considérez l’exemple suivant: le fichier mymodule.py contient des exemples simples d’implémentation d’une variable, d’une fonction et d’une classe :
%%file monmodule.py
"""
Exemple de module python. Contient une variable appelée ma_variable,
Une fonction appelée ma_fonction, et une classe appelée MaClasse.
"""
ma_variable = 0
def ma_fonction():
"""
Exemple de fonction
"""
return ma_variable*2
class MaClasse:
"""
Exemple de classe.
"""
def __init__(self):
self.variable = ma_variable
def set_variable(self, n_val):
"""
Définir self.variable à n_val
"""
self.variable = n_val
def get_variable(self):
return self.variable
Overwriting monmodule.py
On peut importer le module monmodule dans notre programme Python en utilisant import :
import monmodule
monmodule.ma_variable
0
1.10.2.1. La bibliothèque standard et ses modules¶
Une bibliothèque standard Python (Python Standard Library) est une collection de modules qui donne accès à des fonctionnalités de bases : appels au système d’exploitation, gestion des fichiers, gestion des chaînes de caractères, interface réseau, etc.
1.10.2.2. Références¶
The Python Language Reference: http://docs.python.org/2/reference/index.html
The Python Standard Library: http://docs.python.org/2/library/ (Pour une liste complète des modules python)