Python-语法模板大全(常用)
目录
1.怎么存数据
插入Python数据类型.png
变量:
age =10
字符串: 不可变对象
name = "python"
a = "pythonpythonpython"
# 索引和切片
a[0] # index
a[-1]
a[0:3] # slice
a[0:6:2]
a[-1:-7:-1]
a[::-1] # slice reverse
字符串方法详见：https://www.cnblogs.com/haochen273/p/10244032.html#字符串
列表:
[1,2,3,"python"]
a = [1,2,3,"python"]
len(a)
a[0]
[i*2 for i in a]
a.append(50)
a.insert(2,15)
a.extend([5,8,10])
a[0]="java"
"python" in a
a.index("python")
a.count(1)
a.pop(index)
元组:
(1,2,3)（不可以更改.与list类似）
字典:
{"a":100, "b":"666"}
d = {'Michael': 95, 'Bob': 75, 'Tracy': 85}
d['Michael']
d['Adam'] = 67
'Thomas' in d
d.get('Thomas')
d.pop('Bob')
三大容器的遍历方法
a = [1,2,3]
for i in a:
print(i)
b = (1,2,3)
for i in b:
print(b)
c = {"a":10, "b":20, "c":30}
for key,value in dict.items():
print("key = %s, value = %d"%(key,value))
2.怎么用数据
数字操作符：
+、-、*、/、%、//、**
判断循环:
- if判断:
if a>10:
b = a + 20
if b>20:
pass
elif: a>8:
pass
else:
pass
- while循环
while i<5:
# do something
pass
i = i + 1
while true:
pass
- for循环
for i in [1,2,3]:
print(i)
- break和continue的使用
# break:打断全部循环
for i in [1,2,3,4,5]:
print("----")
if i==4:
break
print(i)
# continue： 打断一次循环
for i in [1,2,3,4,5]:
print("----")
if i==4:
continue
print(i)
3.函数
# 位置参数
def person(name, age):
print(name,age)
# 默认参数
def person(name,age=20):
print(name, age)
# 关键字参数
def person(name, age, **kw):
print('name:', name, 'age:', age, 'other:', kw)
person('hao', 20) # name: Michael age: 30 other: {}
person('hao', 20, gener = 'M', job = 'Engineer') # name: Adam age: 45 other: {'gender': 'M', 'job': 'Engineer'}
extra = {'city': 'Beijing', 'job': 'Engineer'}
person('Jack', 24, **extra)
# 命名关键字参数
def person(name, age, *, city='Beijing', job):
print(name, age, city, job)
person('Jack', 24, job = '123')
person('Jack', 24, city = 'Beijing', job = 'Engineer')
# Combination
# 可变 + 关键字参数
def f1(a, b, c=0, *args, **kw):
print('a =', a, 'b =', b, 'c =', c, 'args =', args, 'kw =', kw)
f1(1, 2, 3, 'a', 'b') # a = 1 b = 2 c = 3 args = ('a', 'b') kw = {'x': 99}
f1(1, 2, 3, 'a', 'b', x=99) # a = 1 b = 2 c = 0 d = 99 kw = {'ext': None}
# 默认参数 + 命名关键字参数 + 关键字参数
def f2(a, b, c=0, *, d, **kw):
print('a =', a, 'b =', b, 'c =', c, 'd =', d, 'kw =', kw)
f2(1, 2, d=99, ext=None) # a = 1 b = 2 c = 0 d = 99 kw = {'ext': None}
4. Python核心编程
4.1. 列表生成器
[x * x for x in range(1, 11) if x % 2 == 0]
5. 类和对象
5.1. 定义类的模板
class Student(object):
def __init__(self, name, score):
self.__name = name
self.__score = score
# print(mike)
def __str__(self):
msg = "name: " + self.__name + "score: " + str(self.__score)
return msg
# mike
__repr__ = __str__
# mike()
__call__ = __str__
@property
def name(self):
return self.__name
@name.setter
def name(self, value):
if type(value) == str:
self.__name = value
else:
raise ValueError('Bad name')
@property
def score(self):
return self.__score
@score.setter
def score(self, value):
if 0 <= value <= 100:
self.__score = value
else:
raise ValueError('Bad score')
def final_report(self):
if self.__score >= 90:
level = 'A'
elif self.__score >= 70:
level = 'B'
elif self.__score >= 60:
level = 'C'
else:
level = 'D'
msg = "Your final value is: " + level
return msg
# 调用
mike = Student('mike', 85)
print("-" * 20 + "Print property" + "-" * 20)
print(mike)
print("name: %s" % (mike.name))
print("-" * 30 + "Print methods" + "-" * 20)
print(mike.final_report())
print("-" * 30 + "Print modified infor" + "-" * 20)
mike.name = "Obama"
mike.score = 50
print("-" * 30)
print("modified name: %s" % (mike.name))
--------------------Print property--------------------
name: mikescore: 85
name: mike
------------------------------Print methods--------------------
Your final value is: B
------------------------------Print modified infor--------------------
------------------------------
modified name: Obama
5.2.继承
class SixGrade(Student):
def __init__(self, name, score, grade):
super().__init__(name, score)
self.__grade = grade
# grade是一个只读属性
@property
def grade(self):
return self.__grade
def final_report(self, comments):
# 子类中调用父类方法
text_from_Father = super().final_report()
print(text_from_Father)
msg = "commants from teacher: " + comments
print(msg)
print("-" * 20 + "继承" + "-" * 20)
fangfang = SixGrade('fang', 95, 6)
fangfang.final_report("You are handsome")
print(fangfang.grade)
--------------------继承--------------------
Your final value is: A
commants from teacher: You are handsome
6
5.3 多态
class SixGrade(Student):
pass
class FiveGrade(Student):
pass
def print_level(Student):
msg = Student.final_report()
print(msg)
print_level(Student('from class', 90))
print_level(SixGrade('from subclass-1', 56))
print_level(FiveGrade('from subclass-2', 85))
Your final value is: A
Your final value is: D
Your final value is: B
6. IO文件操作和OS目录操作
OS操作
import os
# 获取当前目录的绝对路径
path = os.path.abspath('.')
# 创建一个目录
os.path.join('/Users/michael', 'testdir')
os.mkdir('/Users/michael/testdir')
# 删除一个目录
os.rmdir('/Users/michael/testdir')
# 拆分路径
os.path.split('/Users/michael/testdir/file.txt') # ('/Users/michael/testdir', 'file.txt')
os.path.splitext('/path/to/file.txt') # ('/path/to/file', '.txt')
# 重命名
os.rename('test.txt', 'test.py')
# 删除文件
os.remove('test.py')
# 列出所有python文件
[x for x in os.listdir('.') if os.path.isfile(x) and os.path.splitext(x)[1]=='.py']
IO文件
| 方法 | 特性 | 性能 |
|---|---|---|
read() |
读取全部内容 | 一般 |
readline() |
每次读出一行内容 | 占用内存最少 |
readlines() |
读取整个文件所有行，保存在一个列表(list)变量中，每行作为一个元素 | 最好(内存足) |
write() |
写文件 |
# 读
# 下面是read()方法的使用，“r”表示read
with open('testRead.txt', 'r', encoding='UTF-8') as f1:
results = f1.read() # 读取数据
print(results)
# 下面是readline()方法的使用，“r”表示read
with open('testRead.txt', 'r', encoding='UTF-8') as f2:
line = f2.readline() # 读取第一行
while line is not None and line != '':
print(line)
line = f2.readline() # 读取下一行
# 下面是readlines()方法的使用，“r”表示read
with open('testRead.txt', 'r', encoding='UTF-8') as f3:
lines = f3.readlines() # 接收数据
for line in lines: # 遍历数据
print(line)
# 写
with open('/User/test.txt', 'w') as f:
f.write('hello')
7. 正则表达式及re模块的使用
主要参考资料为：
6.1. 正则表达式语法
7.2. re模块的使用
内置的 re 模块来使用正则表达式，提供了很多内置函数：
- pattern = re.compile(pattern[, flag]):
- 参数：
- pattern: 字符串形式的正则
- flag: 可选模式，表示匹配模式
- 例子：
import re
pattern = re.compile(r'\d+')
- Pattern的常用方法
import re
pattern = re.compile(r'\d+')
m0 = pattern.match('one12twothree34four')
m = pattern.match('one12twothree34four', 3, 10)
print("-" * 15 + "Match methods" + "-" * 15)
print("found strings: ", m.group(0))
print("start index of found strings: ", m.start(0))
print("end index of found strings: ", m.end(0))
print("Span length of found strigns: ", m.span(0))
s = pattern.search('one12twothree34four')
print("-" * 15 + "Search methods" + "-" * 15)
print("found strings: ", s.group(0))
print("start index of found strings: ", s.start(0))
print("end index of found strings: ", s.end(0))
print("Span length of found strigns: ", s.span(0))
f = pattern.findall('one1two2three3four4', 0, 10)
print("-" * 15 + "findall methods" + "-" * 15)
print("found strings: ", f)
f_i = pattern.finditer('one1two2three3four4', 0, 10)
print("-" * 15 + "finditer methods" + "-" * 15)
print("type of method: ", type(f_i))
for m1 in f_i: # m1 是 Match 对象
print('matching string: {}, position: {}'.format(m1.group(), m1.span()))
p = re.compile(r'[\s\,\;]+')
print("-" * 15 + "Split methods" + "-" * 15)
print("split a,b;c.d: ", p.split('a,b;; c d'))
p1 = re.compile(r'(\w+) (\w+)')
s1 = 'hello 123, hello 456'
def func(m):
return 'hi' + ' ' + m.group(2)
print("-" * 15 + "替换 methods" + "-" * 15)
print(p1.sub(r'hello world', s1)) # 使用 'hello world' 替换 'hello 123' 和 'hello 456'
print(p1.sub(r'\2 \1', s1)) # 引用分组
print(p1.sub(func, s1))
print(p1.sub(func, s1, 1)) # 最多替换一次
结果是:
---------------Match methods---------------
found strings: 12
start index of found strings: 3
end index of found strings: 5
Span length of found strigns: (3, 5)
---------------Search methods---------------
found strings: 12
start index of found strings: 3
end index of found strings: 5
Span length of found strigns: (3, 5)
---------------findall methods---------------
found strings: ['1', '2']
---------------finditer methods---------------
type of method: <class 'callable_iterator'>
matching string: 1, position: (3, 4)
matching string: 2, position: (7, 8)
---------------Split methods---------------
split a,b;c.d: ['a', 'b', 'c', 'd']
---------------替换 methods---------------
hello world, hello world
123 hello, 456 hello
hi 123, hi 456
hi 123, hello 456
