- Python
- 基本数据类型
- 容器
- 列表
- 字典
- 集合
- 元组
- 函数
- 类
- Numpy
- 数组
- 访问数组
- 数据类型
- 数组计算
- 广播
- SciPy
- 图像操作
- MATLAB文件
- 点之间的距离
- Matplotlib
- 绘制图形
- 绘制多个图形
- 图像
Python
python实现的经典的quicksort算法：
1 def quicksort(arr): 2 if len(arr)<=1: 3 return arr 4 pivot = arr[len(arr)/2] 5 left = [x for x in arr if x < pivot] 6 middle = [x for x in arr if x == pivot] 7 right = [x for x in arr if x > pivot] 8 return quicksort(left) + middle + quicksort(right) 9 10 print quicksort([3,6,8,10,1,2,1]) 11 #prints "[1,1,2,3,6,8,10]"
数字：整型和浮点型的使用与其他语言类似。
x = 3 print(type(x))#printd "<type ‘int‘>" print(x) #prints "3" print(x + 1) #Addition;prints "4" print(x - 1) #Subtraction; prints "2" print(x * 2) #Multiplication; prints "6" print(x ** 2) #Expoentiaton; prints "9" x += 1 print(x)# prints "4" x *= 2 print(x) #prints "8" y = 2.5 print(type(y))# prints "<type ‘float‘>" print(y,y + 1,y * 2,y ** 2) #prints "2.5 3.5 5.0 6.25"
注意！！！！ Python 中没有x++和x--的操作符。
布尔型：Python实现了所有的布尔逻辑。
t = True f = False print(type(t)) #prints "<type‘bool‘>" print(t and f ) #logical AND; prints "False" print(t or f )#Logical OR; prints "True" print( not t )#Logical NOT; prints "False" print(t != f) #Logical XOR;prints "True"
字符串：
hello = ‘hello‘ #String literals can use single quotes world = ‘world‘ # pr double quotes; it does not matter, print(hello) #prints "hello" print(len(hello)) #String length; prints "5" hw = hello + ‘ ‘+ world #String concatention print(hw)# prints "hello world " hw12 = ‘%s %s %d‘ % (hello,world,12) #sprintf style string formatting print(hw12)#prints "hello world 12"
字符串对象的方法：
s = "hello" print(s.capitalize()) #Capitalize a string prints "hello" print(s.upper()) #Convert a stirng to upercase; prints "HELLO" print(s.rjust(7))#Righr-justify a string,padding with space; prints " hello" print(s.center(7))#Center a string,padding with space;prints " hello " print(s.replace(‘l‘,‘(ell)‘)) #Replace all instance of one substring with another; #prints "he(ell)(ell)o" print(‘ world‘.strip())#Strip leading and trailing whitespace; prints "world"
容器 Containers
容器类型：列表（lists） 字典（dictionaries） 集合（sets）和元组（tuples）
列表Lists
列表就是python 中的数组，但是列表长度可变，且能包含不同类型元素
xs = [3,1,2] #Create a list print( xs ,xs[2]) #prints "[3,1,2] 2" print(xs[-1]) #Negative indices count from the end of the list; prints "2" xs[2] = ‘foo‘ #Lists can contain elements of different types print(xs) #Prints "[3,1,‘foo‘]" xs.append(‘bar‘)#Add a new element to the end of the list print(xs) #prints x = xs.pop()#Remove and return the last element of the list print(x,xs)#Prints "bar [3,1,‘foo‘]"
切片Slicing : 为了一次性地获取列表中的元素，python 提供了一种简洁的语法，这就是切片。
nums = list(range(5)) #range is a built-in function that creates a list of integers print(nums)#prints "[0,1,2,3,4]" print(nums[2:4])#Get a slice from index 2 to 4 (exclusive); prints ‘[2,3]" print(nums[2:])#Get a slice from index 2 to the end; prints "[2,3,4]" print(nums[:2])#Get a slice from the start to index 2 (exclusive); prints "[0,1]" print(nums[:])#Get a slice of the whole list ; prints "[0,1,2,3,4]" print(nums[:-1])#Slice indices can be negative; prints "[0,1,2,3]" nums[2:4] = [8,9] # Assign a new sublist to a slice print(nums)#prints "[0,1,8,9,4]"
在Numoy数组的内容中，再次看到切片语法。
循环LOOPS：
animals =[‘cat‘,‘dog‘,‘monkey‘] for animal in animals: print(animal) #prints "cat", "dog","monkey",each on its own line.
如果想要在循环体内访问每个元素的指针，可以使用内置的enumerate函数
animals = [‘cat ‘,‘dog‘,‘monkey‘] for idx,animal in enumerate(animals): print(‘#%d: %s‘%(idx + 1,animal)) #prints "#1: cat","#2: dog","#3: monkey",each on its own line
列表推导List comprehensions :在编程的时候，我们常常想要将一个数据类型转换为另一种。
将列表中的每个元素变成它的平方。
nums = [0,1,2,3,4] squares = [] for x in nums: squares.append(x ** 2) print(squares) #Prints [0,1,4,9,16]
使用列表推导：
nums = [0,1,2,3,4] squares = [x ** 2 for x in nums] print(squares) # prints [0,1,4,9,16]
列表推导还可以包含条件：
nums = [0,1,2,3,4] even_squares = [x ** 2 for x in nums if x % 2 == 0] print(even_squares) # prints "[0,4,16]"
字典Dicionaries
字典用来存储（键，值）对，
d = {‘cat‘:‘cute‘,‘dog‘:‘furry‘}#Create a new dictionary with come data
print(d[‘cat‘]) #Get an entry from a dictionary ; prints "cute"
print(‘cat‘ in d) #Check if a dictionary has a given key; prints "Ture"
d[‘fish‘] = ‘wet‘ #Set an entry in a dictionary
print(d[‘fish‘]) # prints "wet"
# print d[‘monkey‘] #KeyError: ‘monkey ‘ not a key of d
print(d.get(‘monkey‘,‘N/A‘)) # Get an element with a default; prints "N/A"
print(d.get(‘fish‘,‘N/A‘))#Get an element with a default ; prints "wet"
del d[‘fish‘] #Remove an element from a dictionary
print(d.get(‘fish‘,‘N/A‘)) # "fish" is no longer a key ;prints "N/A"
循环LOOPS：在字典中，用键来迭代。
d = {‘person‘:2,‘cat‘:4,‘spider‘:8}
for animal in d:
legs = d[animal]
print(‘A %s has %d legs‘ % (animal,legs))
#Prints "A person has 2 legs", " A spider has 8 legs","A cat has 4 legs"
访问键和对应的值，使用items方法：
d = {‘person‘:2,‘cat‘:4,‘spider‘:8}
for animal,legs in d.items():
print(‘A %s has %d legs‘ % (animal,legs))
#prints " A person has 2 legs","A spider has 8 legs","A cat has 4 legs"
字典推导Dictionary comprehensions :和列表推导类似，但是允许你方便地构建字典。
nums = {0,1,2,3,4}
even_num_square = {x:x**2 for x in nums if x % 2 == 0}
print(even_num_square) # prints "{0:0,2:4,4:16}"