Python-语法模板大全(常用)
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2022-07-02 16:53:26
[TOC] 1.怎么存数据 变量: age =10 字符串: name = "python" 列表: [1,2,3,"python"] 元组: (1,2,3)(不可以更改) 字典: {"a":100, "b":"666"} 2.怎么用数据 数字操作符: +、 、 、/、%、//、\ \ 判断循环: ......
目录
1.怎么存数据
- 变量: age =10
- 字符串: name = "python"
- 列表: [1,2,3,"python"]
- 元组: (1,2,3)(不可以更改)
- 字典: {"a":100, "b":"666"}
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
- if判断:
while i<5: # do something pass i = i + 1 while true: pass
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. 类和对象
4.1. 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
4.2.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
4.3 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
5. 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')
6. 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
6.2. 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
- pattern: 字符串形式的正则
- 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
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