¡Escribamos y entendamos el árbol de decisiones en Python desde cero! Parte 2. Conceptos básicos de Python necesarios para generar un árbol de decisiones

¡Hola, Habr! Presento a su atención la traducción del artículo " Python で 0 か ら デ ィ シ ジ ョ ン ツ リ ー を 作 っ て 理解 す る （2. Python プ ロ グ ラ ム 基礎 編） ".



Este artículo es el segundo de una serie. Puedes encontrar el primero aquí .

2.1 Los comentarios se indican con # o '' '(tres comillas simples)

# 
a = 1 #  

'''   
b = c
c = d
'''

2.2 Uso de escritura dinámica (el tipo se determina automáticamente)

#   
# =    
i = 1 #    (int)
f = 2.1 #     (float)
s = "a" #   (string)
b = True #   (boolean)
l = [0,1,2] # , (array) 
t = (0,1,2) #  (tuple)
d = {"a":0, "b":1} # ,  

print(i,f,s,b,l,t,d)
# 1 2.1 a True [0, 1, 2] (0, 1, 2) {'a': 0, 'b': 1}

#    ,  type
print(type(i)) #  <class 'int'>

#   ,    
# ,  , -,    
#       id
print(id(l)) # 00000000000000 (    )
l2 = l #     ,    2  ,    - 1. 
print(id(l2)) # 00000000000000 (  ,    id(l))
#      , ,       l,         l2.
l2.append(1)

2.3 ( . , , )

a = 1 #     1
b = a # b    1 
a = 2 #    2,  b  
a += 1 #     1 (     3)
a -= 1 #     1 (     2)
a *= 2 #       (     4)
a /= 3 #    ⅓   (     1.3333333333333333)
a = 1+2-3*4/5 #    : , , ,  → a  0,6. (,   ,   0.6000000000000001)

2.4

a = 0
#     ,  .
#   , ,   ..
if a == 1:
    # ,      ​​        ,    .
    print(1)
    print(2)
    pass #      
    #    if      
print(3) #     ,     if

#  3

2.4.1

# ,   ,   
if  :
    # program group

#      
#     v   
for v in 
    # program group

#      
while :
    # program group

#      
# (          )
def  ():
    # program group
    #    ,     return
    #     
    return

#     
# print(2)         
# , program group 2      
if a == 1:
    #   program group 1   if a==1:
    print(1)
        #  program group 2   ,    .
        print(2)

2.4.2

a = 1
b = 2
c = 2

#  a  b ,  a  c 
if a==b and a!=c:
    print("  ")

#     b ( =b)  >c (  =)
elif a>=b or a>c:
    print("    b   ")

#     if  elif
else:
    print(" ")

#  " "

2.4.2.1

a = 1
b = 2
#  =b,  v=0,  ,  v=1
v = 0 if a==b else 1
print(v)
#  1 

2.4.3 (for)

for v in [0,1,2,3]: #      [0,1,2,3] .
    #   .      v   
   print(v)
   pass #   
#  0 1 2 3

#  enumerate,         .
for i,v in enumerate([5,3,7,8]):
    # i - , v -  
    print("(",i,v,")")
#  ( 0 5 ) ( 1 3 ) ( 2 7 ) ( 3 8 )

#   zip          .
for v0,v1 in zip([1,2,3,4],[5,6,7,8]):
    # v0      zip,  v1    .
    print("(",v0,v1,")")
#  ( 1 5 ) ( 2 6 ) ( 3 7 ) ( 4 8 )

2.4.4 while

a = 3

#  a    0
while a>=0:
    print(a)
    #   a  1
    a -= 1

#  3 2 1 0

2.4.5

#  :  - function_name, : param1  param2, param2 -   
#  ,    ,        1 (  )
def function_name(param1,param2=1):
    print("p1:",param1,"p2",param2)
    #      param1  param2
    return param1 + param2

#   (     function_name)
#  param1 = 5,  param2   (   )
v = function_name(5)
#  (    print   function_name) p1: 5 p2 1
print(" ",v)()
#  "  6"

2.4.5.1 -,

#   = lambda ( ) : ( ) -     .
f = lambda x: x*x
#     ,      def
v = f(2)
print(v) #  4

2.5

si = "1"   #
sf = "2.3" #
i = 4      # 

#    i  ,   
print(str(i)+si)
# 41

#   -   si   (int),   
print(i+int(si))
# 5

#        (float),     (      float)
print(i+float(sf))
# 6.3

2.6 ,

#  
a = [1,1,2,3,2]              # a=[1,1,2,3,2]
b = [n for n in range(8)]  # b=[0, 1, 2, 3, 4, 5, 6, 7]

# 
#    ,    -1    
v = a[0]  # v=1
v = a[-1] # v=2

# 
a += [4]     # a=[1, 1, 2, 3, 2, 4]
a.append(5)  # a=[1, 1, 2, 3, 2, 4, 5]

#  (  a=[1, 1, 2, 3, 2, 4, 5])
v = a.pop(0) # v=1, a=[1, 2, 3, 2, 4, 5]

#  (  a=[1, 2, 3, 2, 4, 5])
# a[ :  ]
#    ,    a[:],       0,  -  )
c = a[1:3] # c=[2, 3]

# ・ (  = [1, 2, 3, 2, 4, 5])
mx,mi = max(a),min(a) # mx=5, mi=1

#  (mean)、 (median)、  (mode)、 (stdev)、(variance)
# (  a=[1, 2, 3, 2, 4, 5])
from statistics import mean,median,mode,stdev,variance
v = mean(a) # v=2.8333333333333335
v = median(a) # v=2.5
v = mode(a) # v=2
v = stdev(a) # v=1.4719601443879744
v = variance(a) #v=2.1666666666666665

#  (  a=[1, 2, 3, 2, 4, 5])
c = set(a) # c={1, 2, 3, 4, 5}

# Sorted（   ）(  a=[1, 2, 3, 2, 4, 5])
c = sorted(a) # c=[1, 2, 2, 3, 4, 5] ( a   )

# Sort（  ）(  a=[1, 2, 3, 2, 4, 5])
a.sort()      # a=[1, 2, 2, 3, 4, 5]

#     （mapping） (  a=[1, 2, 2, 3, 4, 5])
#  - x: x+2.  x   x+2.
# list    map  
c = list(map(lambda x:x+2,a)) #c=[3, 4, 4, 5, 6, 7]

# 　(  a=[1, 2, 2, 3, 4, 5])
#  - x: x%2==0
#   x、     .     
c = list(filter(lambda x:x%2==0,a)) #c=[2, 2, 4]

#          
# x -  （  ,  -    ）
# xi -   
from functools import reduce
#  x+xi,     （  a=[1, 2, 2, 3, 4, 5]）
c = reduce(lambda x,xi:x+xi,a) #c=17
#  max(xi,x),      （  a=[1, 2, 2, 3, 4, 5]）
c = reduce(lambda x,xi:max(x,xi),a) #c=5

2.7 (dictionary)、

# .  -  , ,  ,   - 
d = {
    " " : [81, 60, 97, 96],
    "" : [80, 78, 75, 96],
    " " : [76, 85, 65, 88],
}
print(d)
#  {' ': [81, 60, 97, 96], '': [80, 78, 75, 96], ' ': [76, 85, 65, 88]}

#    for
d1 = {name:[0,1] for name in [" ",""," "]}
#  {' ': [0, 1], '': [0, 1], ' ': [0, 1]}

#     
a = d[""] # a=[80, 78, 75, 96]

#     （）
d[" "] = [77, 61, 91, 87] # d[" "]=[77, 61, 91, 87]

#  
for k,v in d.items():
    print(k,v)
#    [81, 60, 97, 96]  [80, 78, 75, 96]   [77, 61, 91, 87]

#  、 （    “ ”）
jmx,jmi = max(d[" "]),min(d[" "])
#print(jmx,jmi)

#       
from statistics import mean
#       max       , ,     
#    -        k(   )
kmx = max(d,key=lambda k:mean(d[k])) # kmx=" "

2.8 with open

# with,  

# with   ,    .
# , ,    open,       close 
#   with      open,     with  close  .

# mode - r: 、w: 、a:  
#  ,      open,  f
with open("09_memo.txt",mode="a") as f:
    #   
    f.write("こんにちは\n")

#  
with open("09_memo.txt","r") as r:
    print(r.read())

2.9 random

#   
import random

#    
#                .
#   seed  ,        .
random.seed(0)

#       0   1.
print(random.random()) #  0.8444218515250481

#           .
print(random.randint(1,3)) #     1,2,3

#     
print(random.choice([0,1,2])) #     0,1,2

#     
#      
print(random.sample([0,1,2],2)) #   [1, 2]

#    
#     -      
a = [0,1,2]
random.shuffle(a)
print(a) #  [0, 2, 1]
print(random.sample(a,len(a))) #       sample

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