基礎(chǔ)語法-創(chuàng)新互聯(lián)
1.變量
1.1變量作用
變量是用于存儲(chǔ)數(shù)據(jù)
讓客戶滿意是我們工作的目標(biāo)，不斷超越客戶的期望值來自于我們對這個(gè)行業(yè)的熱愛。我們立志把好的技術(shù)通過有效、簡單的方式提供給客戶，將通過不懈努力成為客戶在信息化領(lǐng)域值得信任、有價(jià)值的長期合作伙伴，公司提供的服務(wù)項(xiàng)目有：域名注冊、虛擬空間、營銷軟件、網(wǎng)站建設(shè)、白云鄂網(wǎng)站維護(hù)、網(wǎng)站推廣。
1.2變量定義規(guī)范
聲明變量
name = "vita"
pep8規(guī)范：等號兩邊要有空格
變量定義規(guī)則
- 變量名只能是字母、數(shù)字、下劃線的任意組合
- 變量名的第一個(gè)字符不能是數(shù)字
- 程序關(guān)鍵字不能是數(shù)字，例如if else while等
變量命名習(xí)慣
駝峰體
AgeOfVita = 27
下劃線
age_of_vita = 27
變量定義的low方式
變量名為中文、拼音 名字 = "vita"
變量名過長 qeqweqwe_qweqweqw_qwewqeq
變量名詞不達(dá)意 a = 23
1.3常量
常量定義
常量即指不變的量，如pai 3.1415926 ,或在程序運(yùn)行過程中不會(huì)改變的量。
Python中沒有專門的語法定義常量，程序員約定用變量名全部大寫代表常量。
python中可自定義一個(gè)不修改的常量的類。
AGE_OF_VITA = 27
Java中定義常量，修改該常量會(huì)報(bào)錯(cuò)
public static final String SUNDAY = "SUNDAY";
c語言中定義常量，修改該常量也會(huì)報(bào)錯(cuò)
const int count = 60;
變量與常量用法示例
在使用中變量和常量沒什么區(qū)別
Python 2.7.16 (v2.7.16:413a49145e, Mar 4 2019, 01:37:19) [MSC v.1500 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license()" for more information.
>>> a = 1
>>> b = a
>>> print(a)
1
>>> print(b)
1
>>> a=2
>>> print(a)
2
>>> print(b)
1
>>>
>>>
>>> A = 10
>>> B=A
>>> print(A)
10
>>> print(B)
10
>>> A=20
>>> print(A)
20
>>> print(B)
10
>>>
2.讀取用戶輸入
name = input("please input your name:")
age = input("please input your age:")
hometown = input("please input your hometown:")
print("your name is:"+name
+ " your age is:"+age
+ " your hometown is:"+hometown)運(yùn)行
E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py
please input your name:vita
please input your age:27
please input your hometown:jl
your name is:vita your age is:27 your hometown is:jl3.注釋
本行注釋
age = input("please input your age:") # age pep8規(guī)范：#號前面至少兩個(gè)空格，后面一個(gè)空格單行注釋
hometown = input("please input your hometown:")
# print age pep8規(guī)范：#號前面無空格，后面一個(gè)空格多行注釋
"""
print age
name hometown
"""
'''
print age
name hometown
pep8規(guī)范：注釋與下面的代碼的空行不能多于兩行
'''
print("your name is:"+name
+ " your age is:"+age
+ " your hometown is:"+hometown)4.數(shù)據(jù)類型
4.1數(shù)字類型
4.1.1介紹
int(整型)
在32位機(jī)器上，整數(shù)的位數(shù)為32位，取值范圍為-2**31~2**31 -1，即-2147483648~214748364
在64位系統(tǒng)上，整數(shù)的位數(shù)為64位，取值范圍為-2**63~2**63-1,即-9223372036854775808~9223372036854775807long(長整型)
跟C語言不同，Python的長整型沒有指定寬度，即python沒有限制長整數(shù)數(shù)值的大小，但實(shí)際上由于內(nèi)存的限制，我們使用的長整數(shù)數(shù)值不可能無限大。注意：
自從Python2.2起，如果整數(shù)發(fā)生溢出，Python會(huì)自動(dòng)把int轉(zhuǎn)換為long，所以現(xiàn)在在long數(shù)據(jù)后面不加字母L也不會(huì)導(dǎo)致嚴(yán)重后果了。
在Python3中沒有int和long的區(qū)分了，全部都是int除了int和long外，還有float浮點(diǎn)型，復(fù)數(shù)型
4.1.2Python2&3之int long
(venvP3) E:\PythonProject\python-test>python2
Python 2.7.16 (v2.7.16:413a49145e, Mar 4 2019, 01:37:19) [MSC v.1500 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> type(2**4)
<type 'int'>
>>> type(2**65)
<type 'long'>
>>> quit()
(venvP3) E:\PythonProject\python-test>python3
Python 3.6.2 (v3.6.2:5fd33b5, Jul 8 2017, 04:57:36) [MSC v.1900 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> type(2**4)
<class 'int'>
>>> type(2**65)
<class 'int'>
>>>4.2字符串
在Python中，加了引號的字符就被認(rèn)為是字符串
4.2.1字符串種類
Name = "vita" # 雙引號
Age = "27" # age是字符串
AgeNum = 27 # age是int
Msg = 'My name is vita,i am 27 years old!' # 一對單引號
# 一對三個(gè)單引號
MsgThree = '''
My name is vita,
i am 27 years old!
'''
# 三個(gè)雙引號
MsgDouThree = """
My name is vita,
i am 27 years old!
"""4.2.2單引號，雙引號，多引號的區(qū)別
單引號和雙引號沒有任何區(qū)別，只是在下面情況下需要考慮單雙引號配合
Msg = "my name is vita,I'm 27 years old"多引號的作用是多行字符串，需要使用多引號
# 一對三個(gè)單引號
MsgThree = '''
My name is vita,
i am 27 years old!
'''
# 三個(gè)雙引號
MsgDouThree = """
My name is vita,
i am 27 years old!
"""4.2.3字符串拼接
字符串可以進(jìn)行“相加”和“相乘”運(yùn)算
>>> name = "vita"
>>> age = "27"
>>> print("your name is:"+name+" your age is:"+age)
your name is:vita your age is:27
>>> print("v"*3)
vvv字符串不能喝整數(shù)拼接
>>> name = "vita"
>>> age = 27
>>> print(name+age)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: must be str, not int4.3布爾型
布爾型就兩個(gè)值，true和false，主要用于邏輯判斷
>>> a =3
>>> b = 5
>>> a>b
False
>>> a<b
True4.4格式化輸出
name = input("input your name:")
age = input("input your age:")
hometown = input("input your hometown:")
msg = '''
------the info of %s is ------
name: %s
age: %s
hometown: %s
------the info of end ------
''' % (name, name, age, hometown)
print(msg)E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py
input your name:vita
input your age:27
input your hometown:jl
------the info of vita is ------
name: vita
age: 27
hometown: jl
------the info of end ------4.5運(yùn)算符
運(yùn)算符種類算數(shù)運(yùn)算符、比較運(yùn)算符、邏輯運(yùn)算符、賦值運(yùn)算符
>>> a = 3
>>> b = 4
>>> a>b and a==3
False
>>> a<b and a==3
True
>>> a<b or a!=3
True
>>> a>b or a==3
True
>>> not a==3
False
>>>4.6流程控制
4.6.1單分支
if 條件成立:
執(zhí)行代碼# _*_coding:utf-8_*_
"""
輸入姓名，性別和年齡，
如果是女生且年齡小于28，輸出我喜歡年輕女孩
"""
name = input("input your name:")
sex = input("input your sex(boy|BOY/girl|GIRL):")
#input()讀入的age是字符串，要轉(zhuǎn)換為int才能與28做大小比較
age = int(input("input your age:"))
if sex.lower() == "girl" and age < 28:
print(name+" i like young girl")E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/singleif.py
input your name:vita
input your sex(boy|BOY/girl|GIRL):GIRL
input your age:26
vita i like young girl4.6.2雙分支
if 條件:
條件滿足，執(zhí)行代碼
else:
條件不滿足，執(zhí)行代碼# _*_coding:utf-8_*_
"""
輸入姓名，性別和年齡，
如果是女生
年齡小于28，輸出我喜歡年輕女孩,
年齡不小于28，輸出年齡比我大也可以
如果不是女生
輸出我不喜歡男生
"""
name = input("input your name:")
sex = input("input your sex(boy|BOY/girl|GIRL):")
#input()讀入的age是字符串，要轉(zhuǎn)換為int才能與28做大小比較
age = int(input("input your age:"))
if sex.lower() == "girl" :
if age < 28:
print(name+" i like young girl")
else:
print("the age is greater than me is also ok!")
else:
print("i do not like boy")E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/singleif.py
input your name:vita
input your sex(boy|BOY/girl|GIRL):girl
input your age:12
vita i like young girl
E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/singleif.py
input your name:vita
input your sex(boy|BOY/girl|GIRL):girl
input your age:28
the age is greater than me is also ok!
E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/singleif.py
input your name:vita
input your sex(boy|BOY/girl|GIRL):boy
input your age:23
i do not like boy4.6.3多分支
if 條件:
滿足條件執(zhí)行代碼
elif 條件:
上面條件不滿足，執(zhí)行這里
elif 條件:
上面條件不滿足，執(zhí)行這里
else:
所有條件都不滿足，執(zhí)行這里# _*_coding:utf-8_*_
"""
輸入姓名，性別和年齡，
如果是女生
年齡小于28，輸出我喜歡年輕女孩,
年齡不小于28，輸出年齡比我大也可以
如果不是女生
輸出我不喜歡男生
"""
name = input("input your name:")
sex = input("input your sex(boy|BOY/girl|GIRL):")
#input()讀入的age是字符串，要轉(zhuǎn)換為int才能與28做大小比較
age = int(input("input your age:"))
if sex.lower() == "girl" :
if age < 28:
print(name+" i like young girl")
else:
print("the age is greater than me is also ok!")
elif sex.lower() == "boy":
print("i do not like boy")
else:
print("your input is not manual human")E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/singleif.py
input your name:vita
input your sex(boy|BOY/girl|GIRL):w
input your age:23
your input is not manual human4.6.4while
while 條件:
執(zhí)行代碼"""
只打印1-10的偶數(shù)
"""
count = 0
while count < 10:
if count%2 == 0:
print(count)
count = count + 1E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py
0
2
4
6
8"""
打印1-10，第五次不打印，6-8打印值的平方
"""
count = 0
while count <= 10:
if count == 5:
pass
elif count>=6 and count<=8:
print(count*count)
else:
print(count)
count = count + 1E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py
0
1
2
3
4
36
49
64
9
104.6.5死循環(huán)(dead loop)
只要運(yùn)行起來，就不再停止,直到把內(nèi)存耗盡
"""
只打印1-10的偶數(shù)
"""
count = 0
while count < 10:
print(count)
# count = count + 1
#注釋掉最后一行，程序一直成立，會(huì)一直運(yùn)行4.6.6循環(huán)終止
break:用于完全結(jié)束一個(gè)循環(huán)，跳出循環(huán)體執(zhí)行循環(huán)后面的語句
continue:終止本次循環(huán)，下次的循環(huán)繼續(xù)
"""
打印1-10，第五次不打印，6-8打印值的平方
"""
count = 0
while count <= 10:
if count == 5:
# 這里一定要記得把count+1,否則count就一直等于5，就死循環(huán)了
count = count + 1
continue
elif count>=6 and count<=8:
print(count*count)
else:
print(count)
count = count + 1
E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py
0
1
2
3
4
36
49
64
9
10"""
打印1-10，第五次不打印，6-8打印值的平方
"""
count = 0
while count <= 10:
if count == 5:
# 這里一定要記得把count+1,否則count就一直等于5，就死循環(huán)了
count = count + 1
break
elif count>=6 and count<=8:
print(count*count)
else:
print(count)
count = count + 1
E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py
0
1
2
3
44.6.7while...else
只有在Python中有while...else
while后面的else指，當(dāng)while循環(huán)正常執(zhí)行完，中間沒有被break中止的話，就會(huì)執(zhí)行else
count = 0
while count <= 3:
if count == 2:
count = count + 1
continue
else:
print(count)
count = count + 1
else:
print("success")
E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py
0
1
3
success
count = 0
while count <= 3:
if count == 2:
count = count + 1
break
else:
print(count)
count = count + 1
else:
print("success")
E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py
0
1本章代碼案例：
"""
猜年齡游戲：
允許用戶最多猜三次，猜了三次后，詢問是都繼續(xù)玩，如果輸入Y，可以繼續(xù)猜三次，否則退出
"""
age = 23
count = 0
while count < 3:
try:
guess_age = int(input("input the age of you think:"))
except ValueError:
print("you should input one number!")
count = count + 1
continue
if guess_age > 23:
print("the age you input is too big!")
elif guess_age < 23:
print("the age you input is too small!")
else:
print("excellent!you are right!")
break
count = count + 1
while count == 3:
your_choice = input("you only have three chances,would you like to continue(Y|y/N|n):")
if your_choice.lower() == "y":
count = 0
elif your_choice.lower() =="n":
break
else:
print("your input is illegal!input again!")運(yùn)行
E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/guessage.py
input the age of you think:2
the age you input is too small!
input the age of you think:45
the age you input is too big!
input the age of you think:33
the age you input is too big!
you only have three chances,would you like to continue(Y|y/N|n):y
input the age of you think:2w
you should input one number!
input the age of you think:24
the age you input is too big!
input the age of you think:55
the age you input is too big!
you only have three chances,would you like to continue(Y|y/N|n):y
input the age of you think:23
excellent!you are right!
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