python 两点曲线_Python自学教程| 3万字详解每个重要知识点（内附视频）

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# comment in separate line  x = x * 5x = x * 5   # multiply by 5; comment in same line# this function is going to divide two variables  # the second value should not be zero  # if it is zero, error is thrown  def divide(first, second):

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str = "# hello world"

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numOfBoxes = 7  ownerName = "Karthik"  print("numOfBoxes= ", numOfBoxes)  print("ownerName= ", ownerName)

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# valid names  numOfBoxes = 7  _num_of_boxes = 10           # this is a different variable than numOfBoxes  _NUM_OF_BOXES = 15   # a different variable as names are case sensitiveownerName = "Karthik"  ownerName2 = "Charan" # different, valid variable# invalid names  2ownerName = "David"    # cannot start with number.                                              # Only letter or underscore in the beginning  owner-name = "Ram"       # no hypen  owner name = "Krish"      # no space allowed                                            # only alpha numeric and underscore

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# different values assigned to many variables  length, width, depth = 5, 8, 7  print(length)  print(width)  print(depth)# same value assigned to many variables  length = width = depth = 5  print(length)  print(width)  print(depth)

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a = 10  b = 6  print (a + b)    # addition  print (a - b)     # subtraction  print (a * b)     # multiplication  print (a / b)      # division  print (a % b)    # modulus  print (a ** b)   # exponentiation  print (a // b)    # floor division

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a = 7  # assign value to a  b = a  # assign value of a into b  c = a + b -2  # calculate an expression and place result into c  b += 2   # equivalent to b = b + 2  b -= 2    # equivalent to b = b - 2  b *= 2   # equivalent to b = b * 2  b /= 2    # equivalent to b = b / 2  b %= 2   # equivalent to b = b % 2  b //= 2   # equivalent to b = b // 2  b **= 2  # equivalent to b = b ** 2  b &= 2   # equivalent to b = b & 2  b |= 2    # equivalent to b = b | 2  b ^= 2    # equivalent to b = b ^ 2  b >>= 2  # equivalent to b = b >> 2  b <<= 2  # equivalent to b = b << 2

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a = 3  b = 7  print(a == b)  # true if a and b are equal  print(a != b)  # true if a and b are not equal  print(a > b)  # true if a is greater than b  print(a < b)  # true if a is less than b  print(a >= b)  # true if a is greater than or equal to b  print(a <= b)  # true if a is less than or equal to b

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a = 3  b = 7  if(a < b):      print("first number is less than second one");  else:      print("first number is greater than or equal to second one")

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a = 5  b = 8  # True if both conditions are true  print(a > 3 and a < 7)  # True if one condition is true  print(a > 6 or b < 7)  # True if given condition is false (inverse of given condition)  print(not(a > 3))

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a = ["hello", "world"]  b = ["hello", "world"]  c = a  # prints true as both are same element  print(a is c)  # prints false as they are two diffent values  # content may be same, but value locations are different  print(a is b)  # comparing the values gives true  print(a == b)  # not negates the comparison result  # if two variables are not same, then result is true  print(a is not c)  print(a is not b)

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a = ["hello", "world"]  # checks if given element is present in the a list  print("world" in a)  # checks if given element is not present in the a list  print("world" not in a)

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a = 1   # binary equivalent of 1 is  1  b = 2   # binary equivalent of 2 is 10  # In case of AND(&) operation, if both bits are 1, set result to one  # in our case, two corresponding bits are not 1  # so, corresponding result is 0  print(a & b)  # OR operation (|), gives 1 if either operands are 1  # The reult of 0 and 1 is 1, 1 and 0 is 1  # hence, a | b gives binary 11 or decimal equivalent of 3  print(a | b)  # XOR (^) returns 1 if only one of the operands is 1  # 1 ^ 1 = 0, 0 ^ 0 = 0, 1 ^ 0 = 1, 0 ^ 1 = 1  # considering a and b, they have only ones in each bit position  print(a ^ b)  # NOT operation negates the bit value  # NOT 0 = 1, NOT 1 = 0  # while negating b, all preceeding zeros are turned to one  # this leads to a negative number  print(~ b)  # zero fill left shift (<# zeros are filled from right, bits are shifted to left  # left most bits fall off  # in this example, we shift the bits of b twice  # 10 (b) shifted twice is 1000 (which is decimal 8)  print(b << 2)  # signed right shift (>>)  # shift the bits to the right, copy leftmost bits to the right  # right most bits fall off  # when we shift b (10) once to the right, it becomes 1  print(b >> 1)

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# a lambda function with the name growth is created  # it takes one argument and increase it by 2  growth = lambda givenLength : givenLength + 2  print(growth(25))  # prints 27  Let us take another example with many parameters:# lambda with the name area is created  # two parameters are passed, who area is calculated  area = lambda length, breadth: length * breadthprint(area(4, 7))  # prints 28

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# the growth lambda we wrote earlier  def growth(n):      return lambda a : a + n  # create a function that would increase by 2  strechTwo = growth(2)  # create a function that would increase by 3  strechThree = growth(3)  print(strechTwo(7))  print(strechThree(7))

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fruits = ["mango", "apple", "grapes"]  print (fruits)

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fruits = ["mango", "apple", "grapes"]  firstFruit = fruits[0]  print (firstFruit)

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fruits = ["mango", "apple", "grapes"]  fruits[0] = "melon"  print (fruits)

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fruits = ["mango", "apple", "grapes"]  print (len(fruits))  # prints 3

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fruits = ["mango", "apple", "grapes"]  for fruit in fruits:      print(fruit)

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fruits = ["mango", "apple", "grapes"]  fruits.append("guava")  print(fruits)  

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fruits = ["mango", "apple", "grapes"]  fruits.pop(1)  print(fruits)  fruits.remove("grapes")  print(fruits)

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# create a class with "class" keyword  class Fruit:      # a property, "name" is created      # the property is assigned with the value "mango"      name="mango"  # let us create an object, "oneFruit" using the above class  oneFruit = Fruit()  # the property of the object "oneFruit" is accessed like this  print(oneFruit.name)

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# create a class with "class" keyword  class Fruit:      # define the init function      def __init__(self, name, color):          self.name = name          self.color = color  # let us create an object, "oneFruit" using the above class  # values are passed to the class  oneFruit = Fruit("mango", "yellow")  # the property of the object "oneFruit" is accessed like this  print(oneFruit.name)  print(oneFruit.color)

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# create a class with "class" keyword  class Fruit:      # define the init function      def __init__(self, name, color):          self.name = name          self.color = color      def makeJuice(self):          print("Made " + self.name + " juice. It will be in " +               self.color + " color.")  # let us create an object, "oneFruit" using the above class  # values are passed to the class  oneFruit = Fruit("mango", "yellow")  # invode object's method  oneFruit.makeJuice()  The property of the object can be modified like this:oneFruit.color = "red"

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lass Vehicle:      def __init__(self, make, color):          self.make = make          self.color = color      def display(self):          print("make= " + self.make + " color= " + self.color)  v = Vehicle("2015", "green")  v.display()

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class Vehicle:      def __init__(self, make, color):          self.make = make          self.color = color      def display(self):          print("make= " + self.make + " color= " + self.color)  # v = Vehicle("2015", "green")  # v.display()  class Car(Vehicle):      def __init__(self, make, color, numOfSeats):          super().__init__(make, color)          self.numOfSeats = numOfSeats      def display(self):          super().display()          print("number of seats= " + str(self.numOfSeats))      def wipeWindshield(self):          print("turned on wiper")  newCar = Car("2019", "orange", 5)  newCar.display()  newCar.wipeWindshield()

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fruitTuple = ("mango", "apple", "grapes")  fruitIter = iter(fruitTuple)  print(next(fruitIter))  print(next(fruitIter))  print(next(fruitIter))  A string can be iterated using iter() method.fruitStr = "mango"  fruitIter = iter(fruitStr)  print(next(fruitIter))  print(next(fruitIter))  print(next(fruitIter))  print(next(fruitIter))  print(next(fruitIter))  print(next(fruitIter)) # last call throws error

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fruitTuple = ("mango", "apple", "grapes")  fruitIter = iter(fruitTuple)  for fruit in fruitTuple:      print(fruit)

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class Fibonacci:      def __iter__(self):          # define first two numbers          self.first = 1          self.second = 2          return self      def __next__(self):          curr = self.first + self.second # find new number          self.first = self.second # shift the previous two numbers          self.second = curr          return curr  fibo = Fibonacci ()  fiboIter = iter(fibo)  print(next(fiboIter))  print(next(fiboIter))  print(next(fiboIter))  print(next(fiboIter))  print(next(fiboIter))

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class Fibonacci:      def __iter__(self):          # define first two numbers          self.first = 1          self.second = 2          return self      def __next__(self):          curr = self.first + self.second # find new number          if (curr <= 50):              self.first = self.second # shift the previous two numbers              self.second = curr              return curr          else:              raise StopIteration  fibo = Fibonacci ()  fiboIter = iter(fibo)  for f in fiboIter:      print(f)

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def func1():      a = 5      print(a)  func1()  print(a)

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a = 5  def func1():      print(a)  func1()  print(a)

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a = 5  def func1():      a = 7      print(a)  func1()  print(a)

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def func1():      global a      a = 10      print(a)  func1()  print(a)

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fruits = ["mango", "apple", "grapes"]  def countStock():      return len(fruits)

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import inventory  print(inventory.countStock())  print(inventory.fruits)

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import inventory as inv  print(inv.countStock())  print(inv.fruits)

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from  inventory import  countStock  print(countStock())  print(fruits)

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import datetime  today = datetime.datetime.now()  print(today)

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import datetime  pastDate = datetime.datetime(2020, 2, 29)  print(pastDate)

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import datetime  pastDate = datetime.datetime(2020, 2, 29)  print(pastDate.strftime("%B"))

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import json  jsonStr = '{ "name" : "mango", "price" : 100, "color" : "yellow" }'  jsonData = json.loads(jsonStr)  print(jsonData["color"])  print(jsonData)

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import json  fruitsDictionary = { "name" : "mango", "price" : 100, "color" : "yellow" }  jsonStr = json.dumps(fruitsDictionary)  print(jsonStr)

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import json  fruitsDictionary = { "name" : "mango", "price" : 100, "color" : "yellow" }  jsonStr = json.dumps(fruitsDictionary, indent=5)  print(jsonStr)

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import json  fruitsDictionary = { "name" : "mango", "price" : 100, "color" : "yellow" }  jsonStr = json.dumps(fruitsDictionary, indent=5, sort_keys=True)  print(jsonStr)

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import re  givenStr = "Hello world, good morning"  outRegex = re.search("^Hello", givenStr)  print(outRegex)

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try:      print(a)  except:      print("error occured, please check if a is defined")

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try:      print(a)  except:      print("error occured, please check if a is defined")  finally:      print("We are here after try and except")

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a = 0  if a == 0:      raise Exception("cannot divide by zero")

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city = input("Where do you live? ")  print("city you live is : " + city)

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tStr = "The fruit {} is {} color."  print(tStr.format("mango", "yellow"))  print(tStr.format("apple", "red"))

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tStr = "The fruit {0} is {1} color. {0} is good for health"  print(tStr.format("mango", "yellow"))  print(tStr.format("apple", "red"))

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tStr = "The fruit {name} is {color} color. {name} is good for health"  print(tStr.format(name = "mango", color = "yellow"))  print(tStr.format(name = "apple", color = "red"))

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a = 4b = 6

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str1 ='hello javatpoint'＃字符串str1   str2 ='你怎么样'#string str2   打印(str1 [0：2])＃使用切片运算符打印前两个字符     打印(str1 [4])＃打印字符串的第4个字符   print(str1 * 2)＃打印两次字符串  打印(str1 + str2)＃打印 str1和str2的串联

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他  Ø 你好，javatpoint你好，javatpoint你好javatpoint你好吗

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l = [1，“ hi”，“ python”，2] 打印(l [3：]) 打印(l [0：2])  打印(l) 打印(l + l)   打印(l * 3)

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[2]  [1，“嗨”] [1，'hi'，'python'，2][1，'hi'，'python'，2，1，'hi'，'python'，2][1，'hi'，'python'，2，1，'hi'，'python'，2，1，'hi'，'python'，2]

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t =(“ hi”，“ python”，2)   打印(t [1：])   打印(t [0：1])   打印(t)   打印(t + t)   打印(t * 3)    打印(type( t))  t [2] =“ hi”

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('python'，2)(“嗨”，)('hi'，'python'，2)(“ hi”，“ python”，2，“ hi”，“ python”，2)('hi'，'python'，2，'hi'，'python'，2，'hi'，'python'，2)追溯(最近一次通话)：中的文件“ main.py”，第8行t [2] =“ hi”;TypeError：“元组”对象不支持项目分配

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d = {1：'Jimmy'，2：'Alex'，3：'john'，4：'mike'} print(“第一个名称为” + d [1]) print(“第二个名称为” + d [ 4])   打印(d)   打印(d.keys())   打印(d.values())

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第一个名字是吉米第二名叫麦克{1：“吉米”，2：“亚历克斯”，3：“约翰”，4：“麦克”}[1、2、3、4]['Jimmy'，'Alex'，'john'，'mike']

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a = 10b = 20

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如果(b> a)：    打印(b大于a)

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b大于a

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如果(a> b)：    打印(“ a大于b”)

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如果(a> b)：    打印(“ a大于b”)其他：    打印(“ b大于a”)

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b大于a

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a = 10b = 20c = 30

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如果(a> b)和(a> c)：    打印(“ a是最大的”)省略号(b> a)和(b> c)：    打印(“ b是最大的”)其他：    打印(“ c是最大的”)

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c是最大的

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l1 = [10,20,30,40,50]

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如果l1 [0] == 10：    l1 [0] = 10011

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[100,20,30,40,50]

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i = 1而(i <= 5)：    打印(i)    i = i + 1

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1个2345

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i = 1n = 2而(i <= 10)：    打印(n，“ *”，i，“ =”，n * i)    i = i + 1

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2 * 1 = 22 * 2 = 42 * 3 = 62 * 4 = 82 * 5 = 102 * 6 = 122 * 7 = 142 * 8 = 162 * 9 = 182 * 10 = 20

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li = [1,2,3,4,5]i = 0当i     l1 [1] = l1 [i] +100    i = i + 111

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[101,102,103,104,105]

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l1 = [“蓝色”，“绿色”，“红色”]对于我在l1    打印(i)

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蓝色 绿色 红

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颜色= [“绿色”，“黄色”，“粉红色”]项目= [“椅子”，“书”，“电话”]对于我的颜色：    对于项目中的j：        打印(i，j)

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绿色椅子绿皮书绿色电话黄色椅子黄皮书黄色电话粉色椅子粉红色的书粉色手机

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f = open("fruits.txt")

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f = open("fruits.txt", "rt")

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f = open("fruits.txt")  print(f.read())

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f = open("fruits.txt")  print(f.readline())  print(f.readline())

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f = open("fruits.txt")  for line in f:      print(line)

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f = open("fruits.txt")  for line in f:      print(line)  f.close()

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f = open("fruits.txt", "a")  f.write("guava is green")  f.close()  f = open("fruits.txt")  for line in f:      print(line)  f.close()

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import os  os.remove("fruits.txt")

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import os  filename = "fruits.txt"  if os.path.exists(filename):      os.remove()  else:      print(filename + " does not exist")

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import os  os.rmdir("unwantedFolder")

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 def add_10(x)：     回报(10 + x)

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add_10(5)

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15

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 ＃这是一条评论counter = 100＃这是一个遵循代码的注释                  ＃这是空格后的注释text =“＃这不是注释，因为井号位于引号内。”

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>>> 2 + 24>>> 50-5 * 430>>>(50-5 * 4)/ 65>>> 8/51.6

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>>> 16/35.333333333333334>>> 16 // 35>>> 16％31个

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>>> 5 ** 225>>> 3 ** 481

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>>>高度= 20>>>宽度= 9 * 5

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>>>税= 12.5 / 100>>>价格= 110.50>>>价格*税13.8125＃这是最后打印的值，因此分配给_>>>价格+ _124.3125＃现在这成为最后的打印值，因此分配给_>>> round(_，2)＃这是将值四舍五入到小数点后两位的命令124.31