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Super Kai (Kazuya Ito)
Super Kai (Kazuya Ito)

Posted on • Edited on

range in Python

#python #range #iterableunpacking #forloop

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*Memos:

  • My post explains enumerate().
  • My post explains zip().
  • My post explains variable assignment.
  • My post explains iterable unpacking in variable assignment.
  • My post explains * for iterable unpacking in variable assignment.
  • My post explains [] and () for variables in variable assignment.
  • My post explains [] and () for variables in for statement.

range() can create the iterable object of numbers between [start, stop) as shown below:

*Memos:

  • The 1st argument is start or stop(Required-Type:int).
    • It's a start index(inclusive) or stop index(exclusive).
    • Don't use start= or stop=.
  • The 2nd argument is stop(Optional-Type:int). *Don't use stop=.
    • It's a stop index(exclusive).
  • The 3rd argument is step(Optional-Default:1-Type:int):
    • It's the interval of elements.
    • It cannot be 0.
    • Don't use step=.
  • Only if one argument is set, the 1st argument is stop, then the iterable object [0, stop) is created.
  • A range object doesn't get MemoryError because it always takes the same small amount of memory and it's not an iterator. 
v = range(4) v = range(0, 4) v = range(0, 4, 1) print(v) # range(0, 4)  print(type(v)) # <class 'range'>  print(v.start, v.stop, v.step) # 0 4 1  print(v[0], v[1], v[2], v[3]) # 0 1 2 3  print(list(v)) # [0, 1, 2, 3]
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v1 = range(4) print(v1) # range(0, 4)  v2 = v1[1:3] print(v2) # range(1, 3)  print(list(v2)) # [1, 2]
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print(list(range(-5, 12, 3))) # [-5, -2, 1, 4, 7, 10]  print(list(range(12, -5, -3))) # [12, 9, 6, 3, 0, -3]  for i in range(4): # for i in range(0, 4): # for i in range(0, 4, 1):  print(i) # 0 # 1 # 2 # 3  for i in range(-5, 12, 3): print(i) # -5 # -2 # 1 # 4 # 7 # 10  for i in range(12, -5, -3): print(i) # 12 # 9 # 6 # 3 # 0 # -3
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fruits = ["Apple", "Orange", "Banana", "Kiwi", "Lemon", "Mango"] for i in range(4): # for i in range(0, 4): # for i in range(0, 4, 1):  print(fruits[i]) # Apple # Orange # Banana # kiwi  for i in range(1, 6, 2): print(fruits[i]) # Orange # Kiwi # Mango  for i in range(5, 0, -2): print(fruits[i]) # Mango # Kiwi # Orange
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print(list(zip(range(4), range(-5, 12, 3), range(12, -5, -3)))) # [(0, -5, 12), (1, -2, 9), (2, 1, 6), (3, 4, 3)]  print(list(zip(range(4), range(-5, 12, 3), range(12, -5, -3)))[0]) # (0, -5, 12)  i, j, k = list(zip(range(4), range(-5, 12, 3), range(12, -5, -3)))[0] print(i, j, k) # 0 -5 12  for i, j, k in zip(range(4), range(-5, 12, 3), range(12, -5, -3)): print(i, j, k) # 0 -5 12 # 1 -2 9 # 2 1 6 # 3 4 3
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enum = enumerate print(list(enum(zip(range(4), range(-5, 12, 3), range(12, -5, -3)), 7))) # [(7, (0, -5, 12)), (8, (1, -2, 9)), (9, (2, 1, 6)), (10, (3, 4, 3))]  print(list(enum(zip(range(4), range(-5, 12, 3), range(12, -5, -3)), 7))[0]) # (7, (0, -5, 12))  i, jkl = \ list(enum(zip(range(4), range(-5, 12, 3), range(12, -5, -3)), 7))[0] print(i, jkl) # 7 (0, -5, 12)  i, (j, k, l) = \ list(enum(zip(range(4), range(-5, 12, 3), range(12, -5, -3)), 7))[0] print(i, j, k, l) # 7 0 -5 12  for i, jkl in enum(zip(range(4), range(-5, 12, 3), range(12, -5, -3)), 7): print(i, jkl) # 7 (0, -5, 12) # 8 (1, -2, 9) # 9 (2, 1, 6) # 10 (3, 4, 3)  for i, (j, k, l) \ in enum(zip(range(4), range(-5, 12, 3), range(12, -5, -3)), 7): for i, [j, k, l] \ in enum(zip(range(4), range(-5, 12, 3), range(12, -5, -3)), 7): print(i, j, k, l) # 7 0 -5 12 # 8 1 -2 9 # 9 2 1 6 # 10 3 4 3
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