Summary of basic knowledge about python3 learning
1. Data type
1. Number
2. Boolean value
True or False
Variable naming rules:
Variable name can only be any combination of letters, numbers or underscores
- The first character of the variable name cannot be a number
- The variable name cannot be a keyword (for example: and, or,
三, String splicing
1. Use the plus sign (+)
name = "Tom"age = 25print(name + "s age is " + str(age)) #输出：Toms age is 25
2. String formatting
name = = 25( %
4. Lists and Tuples
1. List
Create a list
str_list = ['Tom','Lucy','Mary'] 或者 str_list = list(['Tom','Lucy','Mary'])
Index (access a value in the list)
str_list[0]
Append (add elements to the end)
str_list.append('lilei')print(str_list)#输出：['Tom', 'Lucy', 'Mary', 'lilei']Insert (add an element at the specified position)
str_list.insert(1,'lilei')print(str_list)#输出：['Tom', 'lilei', 'Lucy', 'Mary']
Delete (delete the specified element)
str_list.remove('Lucy')print(str_list)#输出：['Tom', 'Mary']Slice
str_list = [3,4,5,6,7,8,9] new_1 = str_list[1:3] #从索引1开始取，取到索引3 new_2 = str_list[0:6:2] #从索引0开始取，每两位一取，到第6位为止 new_3 = str_list[-2:] # 取后面2个数 new_4 = str_list[:3] # 取前面3个数 new_5 = str_list[::3] #所有数，每3个取一个 print(new_1,new_2,new_3,new_4,new_5) #输出：[4, 5] [3, 5, 7] [8, 9] [3, 4, 5] [3, 6, 9]
2. Tuple
Creating tuples
age = (18,25,33) 或者 age = tuple((18,25,33))
5. Dictionary
Use key-value storage method
Create dictionary
phone = {
'张三':'13075632152',
'李四':'15732015632',
'王五':'13420321523',
}Get the value of the key in the dictionary
print(phone['张三']) #如果key不存在，会报错，key用中括号装print(phone.get('老黄')) #如果key不存在，返回None,key用小括号装#输出：13075632152 # None
Assignment
phone[] = phone[] =
删除
phone.pop('张三') #第一种方法del phone['李四'] #第二种方法phone.popitem() #随机删除某一个
遍历
for key in phone:
print(key,phone[key])
#输出：
# 王五 13420321523
# 张三 13075632152
# 李四 15732015632多级嵌套
phone = {
'人事部':{'老张':'13700112233','老李':'13432023152'},
'财务部':{'小丽':'13230555666','小映':'13723688888'},
'技术部':{'老罗':'13866666333'}
}
print(phone['人事部']['老李'])
#输出：13432023152六、if语句
1、if...else
age = 16
if age <18:
print('你还未成年呢')
else:
print('你已经成年了')2、if...elif....else
score = 85
if score > 0 and score< 60:
print('你的成绩不及格')
elif score >= 60 and score <80:
print('你的成绩及格了')
elif score>=80 and score<90:
print('你的成绩良好')
else:
print('你的成绩优秀')七、while循环
i=0
num=0
while i<=100:
num+=i
i+=1
print('1-100累加等于%d'%num)八、for...in循环
num = []
for i in range(10):
num.append(i)
print(num)
#输出：[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]九、用户交互(input)
name = input('请输入你的名字：') height = input('请输入你的身高：') print('%s的身高%s厘米' %(name,height))
十、文件基本操作
打开文件：f = open('文件路径'，'模式') 或者 with open('文件路径','模式') as f:
模式：
r：以只读方式打开文件
w：打开一个文件只用于写入。如果该文件已存在则将其覆盖。如果该文件不存在，创建新文件。
a：打开一个文件用于追加。如果该文件已存在，文件指针将会放在文件的结尾。也就是说，新的内容将会被写入到已有内容之后。如果该文件不存在，创建新文件进行写入。
w+：打开一个文件用于读写。(文件一打开就清空了，还能读到东西吗？)
a+：打开一个文件用于读写。
读文件：
read() readlines() readline() 的用法
f = open('d:/test.txt','r') #以只读方式打开文件
print(f.read()) #read()一次读取文件的全部内容
for line in f.readlines(): #readlines()读取整个文件，并按行存进列表
print(line.strip('\n')) #去掉行尾的'\n'
while 1:
line = f.readline() #readline()每次只读取一行
print(line.strip('\n'))
if not line:
break
f.close() #关闭文件写文件：
f =open('d:/test.txt','a') f.write('hello,boy!\n') f.close()
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