Python basic knowledge data type string operation if statement is not usage for loop while loop

Python all data types are objects

print(type(123))print(type(4545.666))print(type(1323.))print(type(‘adbn‘))

<class ‘int‘><class ‘float‘><class ‘float‘><class ‘str‘>

All data types are objects

print(type([1,2,2,3,4,5,56,‘a‘,‘b‘]))print(type((1,‘xddfsdfd‘)))print(type(set([‘s‘,‘rff‘,‘dd‘])))print(type({‘a‘: 1, ‘b‘: 2}))

<class ‘list‘><class ‘tuple‘><class ‘set‘><class ‘dict‘>

function is also an object variable also available in Chinese

def func(a,b,c):    print(a,b,c)print(type(func))啊 = funcprint(type(啊))a = funcprint(type(a))

<class ‘function‘><class ‘function‘><class ‘function‘>

The type of string is the module

import stringprint(type(string))

<class ‘module‘>

A class that is not instantiated is called a type instantiation object called Class

class MyClass(object) :        passprint(type(MyClass))my_class = MyClass()print(type(my_class))

<class ‘type‘><class ‘__main__.MyClass‘>

Exception handling, variables must be defined before they are used

try:    x = 100    print(x)except NameError:    print("NameError: ‘x‘ is not define")

Common string processing string cannot be changed

import strings = ‘abc‘s[0] = ‘sd‘

---------------------------------------------------------------------------TypeError                                 Traceback (most recent call last)<ipython-input-1-ce449e8a2e6b> in <module>()      2       3 s = ‘abc‘----> 4 s[0] = ‘sd‘TypeError: ‘str‘ object does not support item assignment

Remove whitespace action

import strings = ‘  hjh 黄金进口件 你看见画江湖 mjjkj ‘# 去除左右空格print(s.strip())# 去除左边空格print(s.lstrip())# 去除右边空格print(s.rstrip())# 输出原来的字符串print(s)

hjh 黄金进口件 你看见画江湖 mjjkjhjh 黄金进口件 你看见画江湖 mjjkj   hjh 黄金进口件 你看见画江湖 mjjkj  

Connection string

s1 = ‘abc‘s2 = ‘def‘print(s1 + "\n" + s2)

abcdef

Uppercase and lowercase conversions

s = ‘abc def‘print(s)#把所有字符变成大写print(s.upper())# 把所有字符变大写后变回去print(s.upper().lower())# 首字母大写print(s.capitalize())

abc defABC DEFabc defAbc def

Location comparison

s1 = ‘abcdefg‘s2 = ‘lalalal‘print(s1.index(‘f‘))print(s1.index(‘fg‘))print(s2.index(‘alal‘))# 找不到时会报错需要异常处理try:    print(s1.index(‘jjj‘))except ValueError:    pass

551

Comparing strings

s1 = ‘ddd‘s2 = ‘sss‘print(s1 == s2)print(s1 < s2)print(s1 > s2)

FalseTrueFalse

String length

601

Empty string differs from None

s = ‘‘if s is None:    print(‘None‘)p = Noneif p is None:    print(‘p is None‘)

p is None

Segmentation of strings

s = ‘abc,def,ghi‘d = ‘abc..def..ghi‘splitted = s.split(‘,‘)print(type(splitted))print(splitted)# 可以按照任意分隔符切分d1 = d.split(‘..‘)print(type(d1))print(d1)# 可以按行分割s1 = """ddddddggggghhhyyyyyjj"""# 方法一按照换行符分割print(s1.split(‘\n‘))# 方法二直接使用按行分割的方法print(s1.splitlines())#区别 按照换行符分割的特点是数量 只与换行符有关 而且使用方法不会捕捉到最后一个换行符

<class ‘list‘>[‘abc‘, ‘def‘, ‘ghi‘]<class ‘list‘>[‘abc‘, ‘def‘, ‘ghi‘][‘ddd‘, ‘dddgg‘, ‘ggg‘, ‘hhh‘, ‘yy‘, ‘yyy‘, ‘jj‘, ‘‘][‘ddd‘, ‘dddgg‘, ‘ggg‘, ‘hhh‘, ‘yy‘, ‘yyy‘, ‘jj‘]

Connection of strings

s = [‘ddd‘, ‘dddgg‘, ‘ggg‘, ‘hhh‘, ‘yy‘, ‘yyy‘, ‘jj‘]# 使用空字符作为连接字符print(‘‘.join(s))print(‘\n‘)# 使用换行符作为连接对象print(‘\n‘.join(s))print(‘\n‘)# 使用短线作为连接对象print(‘-‘.join(s))

ddddddggggghhhyyyyyjjddddddggggghhhyyyyyjjddd-dddgg-ggg-hhh-yy-yyy-jj

Common judgments

s = ‘assddf‘# 判断是不是以字符a开头print(s.startswith(‘a‘))# 判断是不是以字符ass开头print(s.startswith(‘ass‘))# 判断是不是以字母s开头print(s.startswith(‘s‘))# 判断以...结尾print(s.endswith(‘ddf‘))# 判断是不是数字字母的组合print(‘12333hjhjhdas‘.isalnum())print(‘\t212133kjhjdashkjdas‘.isalnum())# 判断是不是纯字母的形式print(‘sjas‘.isalpha())# 判断是不是数字print(‘asada‘.isdigit())# 判断是不是所有单词以大写字母开头print(‘Hello World‘.istitle())

TrueTrueFalseTrueTrueFalseTrueFalseTrue

Convert numeric strings to each other

print(str(5))print(str(5.))print(str(55645.545))print(str(-5454.5454))print(int(‘5656‘))print(float(‘5454.544‘))print(float(‘555.566‘))# 可以指定转换类型  默认是10进制print(int(‘1010101010001‘, 2))print(int(‘abcdef‘, 16))print(int(‘77421‘, 8))

55.055645.545-5454.545456565454.544555.56654571125937532529

String characters convert to each other

s = ‘asdf‘l = list(s)print(l)

[‘a‘, ‘s‘, ‘d‘, ‘f‘]

If judgment

a = 100b = 200c = 300if a == 100:    print(a)elif b == 200:    print(b)else:    print(c)

100

The judgment of None

x = Noneif x is None :    print(‘None‘)else:    print(‘not None‘)

None

For loop

# range(开始数,结束数,间隔)for i in range(0, 30, 5):    print(i)# 不指定间隔时间隔是1for i in range(5,10):    print (i)

051015202556789

While loop

s = 0i = 1while i <= 100:    s += i    i += 1print(s)

5050

About pass and continue and the use of break

for i in range(0, 100):    if i < 10:        pass    elif i < 30:        continue    elif i < 35:        print(i)    else:        break

Definition of a function

def func_name(arg1, arg2):    print(arg1, arg2)    return arg1, arg2def func_name0(arg1, arg2):    print(arg1, arg2)    return arg1 + arg2r = func_name(1, 2)print(type(r))# 可以说是是一个listprint(r[0],r[1])print(func_name0(3, 5))

1 2<class ‘tuple‘>1 23 58

function can specify a default value at the parameter position

def func(x, y = 500):    return x + y# 当调用时有全部参数时就会使用参数print(func(100,800))# 当有一个值未指定时,就会使用默认值print(func(100))

900600

Function arguments can be reversed position

def func(x, y = 500):    print(‘x = ‘, x)    print(‘y = ‘, y)    return x + yprint(func(100))print(func(y = 300, x = 200))print(func(x = 400))

x =  100y =  500600x =  200y =  300500x =  400y =  500900

Variable parameters of a function

# 表示从第一个参数开始所有参数都放到数组里去def func(name, *numbers):    # 类型是只读数组原族    print(type(numbers))    print(numbers)    return ‘Done‘func(‘Tom‘, 1, 2, 3, 4)

<class ‘tuple‘>(1, 2, 3, 4)‘Done‘

Python basic knowledge data type string operation if statement is not usage for loop while loop