Python is an object-oriented , interpreted, dynamically typed computer programming language
- Interpreted: The program does not need to be compiled into binary code, but compiles the statements one by one at execution time
- Dynamic typing: During program execution, the type of a variable can be changed
1. Simple example
temp = input ( "Guess a number: " ) guess = int (temp) if guess == 8 : print ( "guessed correctly" ) else : print ( "wrong" )
result:
2. Data type
1) 150000 == 15e4 //return true. The right side is e notation, e represents 10, and the whole represents the 4th power of 15*10
15e-4 //The whole represents 15*10 to the power of -4
2）
def type_test():
print(type(10)) #<class 'int'>
print(type(10.12)) #<class 'float'>
print(type("werrwer")) #<class 'str'>
print(type(True)) #<class 'bool'>
print(isinstance("hhhh",str)) #True
print(isinstance("hhhh",int
)) #False
3. Operator
def yunsuanfu ():
a = b = c = d = 10
a+= 1 # a=a+1
b-= 3 # b=b-3
c*= 10 # c=c*10
d/= 8 # d=d/8
print ( a) # 11
print (b) # 7
print (c) # 100
print (d) # 1.25
print (b// 3 ) # 7//3=2 Quotient
print (b % 3 ) # 7%3=1 remainder
print ( 3 ** 2 ) #3 to the power of 2 = 9 exponentiation
print (-
3 ** 2 ) # 3 to the power of 2
print ((- 3 )** 2 ) # -3 to the power of 2
3. The priority of various operation symbols
The top of the tower has the highest priority
4、break、continue
1) break: Once the i value that satisfies the condition is encountered, it will jump out of the entire for loop and terminate the loop
for i in range(10):
if i%2 != 0:
print(i)
break
else:
print("===========")
2) continue: After meeting the conditions, jump out of the if and else judgments, that is, do not judge the else, and continue from the for loop to the next loop
for i in range(10):
if i%2 != 0:
print(i)
continue
else:
print("===========")
5、函数使用
1）向列表中增/删数据，三种方法
增加：append、extend、insert
member=['哈哈哈哈',123,[123,34,2],'啦啦啦']
member.append('孩子1') #单个插入到列表中
print(member)
member.extend(['孩子2', '爸爸', '妈妈']) #要给你一个列表扩展另一个列表
print(member)
member.insert(0, '牡丹') #指定插入位置
print(member)
删除：remove、del、pop
member=['哈哈哈哈', '孩子', '爸爸', '妈妈', '爷爷']
member.remove('孩子') #删除'孩子'这个数据
print(member)
del(member[1]) #删除列表索引为1的数据
print(member)
member.pop() #删除列表最后一个数据
print(member)
member.pop(1) #删除 列表下标为1 的数据
print(member)
print(member * 3) #将列表数据复制添加三遍
print(member[1:4]) #分片取列表数据 从下标1开始到下表4 结束，不包括下标4，即下表标
print(member[:4]) #从下表0开始，到4结束
print(member[1:]) #从下表1开始，到最后一个
2）、排序sort、sorted,,,,,reverse
list = [5, 23, 45, 23, 34, 1, 77, 89, 56, 34, 5, 3]
list.sort()
print(list)
print(sorted(list, reverse=True))
list.reverse()
print(list)
sort、sorted均接受 reverse=True or False 这个参数，表示排序的升降顺序
2、对元素指定的某一部分进行排序,关键字排序
s = ['Chr1-10.txt','Chr1-1.txt','Chr1-2.txt','Chr1-14.txt','Chr1-3.txt','Chr1-20.txt','Chr1-5.txt']
我想要按照-后的数字的大小升序排序。要用到key
sorted(s, key=lambda d : int(d.split('-')[-1].split('.')[0]))
['Chr1-1.txt', 'Chr1-2.txt', 'Chr1-3.txt', 'Chr1-5.txt', 'Chr1-10.txt', 'Chr1-14.txt', 'Chr1-20.txt']
这就是key的功能，制定排序的关键字，通常都是一个lambda函数，当然你也可以事先定义好这个函数。如果不讲这个关键字转化为整型，结果是这样的：
sorted(s, key=lambda d : d.split('-')[-1].split('.')[0])
['Chr1-1.txt', 'Chr1-10.txt', 'Chr1-14.txt', 'Chr1-2.txt', 'Chr1-20.txt', 'Chr1-3.txt', 'Chr1-5.txt']
这相当于把这个关键字当做字符串了，很显然，在python中，'2' > '10'
你可以定制你想要的key, 如 key = lambda x : len(x) 按照序列的长度去排序。key= lambda x : (x[1], x[0]) 按二个元素，再第一个 等等。。。
3）、count、index、
member = [2323, 123, 111, 222, 444, 888, 100,123, '123']
print(member.count(123)) # 列表中123出现的次数 输出：3
print(member.index(123)) #列表中 123 出现第一次的下标
print(member.index(123, 2, 8)) #123在下标1到8的数据片段中第一次出现的位置
4）、列表拷贝
list2 = list[:]
list1 = list #list1与list数据是指向同一个
list2 = list[:] #拷贝（备份）
list.reverse() #list反转
print(list1) #与list同步，反转后的list
print(list2) #list反转前的数据