li = [[]] * 3
  print(li)
  # Out: [[], [], []]

  li[0].append(1)
  print(li)
  # Out: [[1], [1], [1]]

  li = []
  element = [[]]
  li = element + element + element
  print(li)
  # Out: [[], [], []]
  element.append(1)
  print(li)
  # Out: [[1], [1], [1]]

  li = [[]] * 3
  print([id(inner_list) for inner_list in li])
  # Out: [6830760, 6830760, 6830760]

li = [[] for _ in range(3)]

  print([id(inner_list) for inner_list in li])
  # Out: [6331048, 6331528, 6331488]

  for i in range(len(tab)):
    print(tab[i])

  for elem in tab:
  print(elem)

  for i, elem in enumerate(tab):
    print((i, elem))

  if (var == True):
    # 當(dāng)var是：True、1、 1.0、 1L時(shí)if條件成立
  if (var != True):
    # 當(dāng)var不是 True 和 1 時(shí)if條件成立
  if (var == False):
    # 當(dāng)var是 False 或者 0 (or 0.0, 0L, 0j) if條件成立

  if (var == None):
    # var是None if條件成立

  if var:
    # 當(dāng)var非空(None或者大小為0)對(duì)象 string/list/dictionary/tuple, non-0等if條件成立

  if not var:
    # 當(dāng)var空(None或者大小為0)對(duì)象 string/list/dictionary/tuple, non-0等if條件成立

  if var is True:
    # 只有當(dāng)var時(shí)True時(shí) if條件成立 1也不行

  if var is False:
    # 只有當(dāng)var時(shí)False時(shí) if條件成立 0也不行

  if var is None:
  # 和var == None 一致

  if os.path.isfile(file_path):
    file = open(file_path)
  else:
    # do something

  try:
    file = open(file_path)
  except OSError as e:
    # do something

with open(file_path) as file:

```
  class Car(object):
    color = "red"
    wheels = [Wheel(), Wheel(), Wheel(), Wheel()]
```

```
  class Car(object):
    def __init__(self):
      self.color = "red"
      self.wheels = [Wheel(), Wheel(), Wheel(), Wheel()]
```

**函數(shù)默認(rèn)參數(shù)**

```
def foo(li=[]):
  li.append(1)
  print(li)

foo([2])
# Out: [2, 1]
foo([3])
# Out: [3, 1]
```

```
foo()
# Out: [1] As expected...

foo()
# Out: [1, 1] Not as expected...
```

```
def foo(li=None):
  if not li:
    li = []
  li.append(1)
  print(li)

foo()
# Out: [1]

foo()
# Out: [1]
```

```
x = []
foo(li=x)
# Out: [1]

foo(li="")
# Out: [1]

foo(li=0) 
# Out: [1]
```

```
def foo(li=None):
  if li is None:
    li = []
  li.append(1)
  print(li)

foo()
# Out: [1]
```

**在遍歷時(shí)修改**

  alist = [0, 1, 2]
  for index, value in enumerate(alist):
    alist.pop(index)
  print(alist)
  # Out: [1]

  # Iteration #1
  index = 0
  alist = [0, 1, 2]
  alist.pop(0) # removes '0'

  # Iteration #2
  index = 1
  alist = [1, 2]
  alist.pop(1) # removes '2'

  # loop terminates, but alist is not empty:
  alist = [1]

  alist = [1,2,3,4,5,6,7]
  for index, item in reversed(list(enumerate(alist))):
    # delete all even items
    if item % 2 == 0:
      alist.pop(index)
  print(alist)
  # Out: [1, 3, 5, 7]

  >>> -8 is (-7 - 1)
  False
  >>> -3 is (-2 - 1)
  True

  >>> (255 + 1) is (255 + 1)
  True
  >>> (256 + 1) is (256 + 1)
  False

>>> 'python' is 'py' + 'thon'
True  

>>> 'this is not a common string' is 'this is not' + ' a common string'
False
>>> 'this is not a common string' == 'this is not' + ' a common string'
True

  i = 0
  a = [i for i in range(3)]
  print(i) # Outputs 2

  i = 0
  a = [i for i in range(3)]
  print(i) # Outputs 0

  i = 0
  for i in range(3):
    pass
  print(i) # Outputs 2

if a == 3 or b == 3 or c == 3:

if a or b or c == 3: # Wrong

if a == 3 or b == 3 or c == 3: # Right Way

if any([a == 3, b == 3, c == 3]): # Right

if any(x == 3 for x in (a, b, c)): # Right

if 3 in (a, b, c): # Right