Python簡明入門教程

2020-01-04 17:58:33

字體：大中小

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這篇文章主要介紹了Python簡明入門教程,較為詳細的分析了Python的基本概念及語法基礎,有助于Python初學者更好的掌握Python的基本語法與使用技巧,需要的朋友可以參考下

本文實例講述了Python簡明入門教程。分享給大家供大家參考。具體如下：

一、基本概念

1、數

在Python中有4種類型的數——整數、長整數、浮點數和復數。

(1)2是一個整數的例子。

(2)長整數不過是大一些的整數。

(2)3.23和52.3E-4是浮點數的例子。E標記表示10的冪。在這里，52.3E-4表示52.3 * 10-4。

(4)(-5+4j)和(2.3-4.6j)是復數的例子。

2、字符串

(1)使用單引號(')

(2)使用雙引號(")

(3)使用三引號('''或""")

利用三引號，你可以指示一個多行的字符串。你可以在三引號中自由的使用單引號和雙引號。例如：

'''This is a multi-line string. This is the first line.

This is the second line.

"What's your name?," I asked.

He said "Bond, James Bond."

'''

(4)轉義符

(5)自然字符串

自然字符串通過給字符串加上前綴r或R來指定。例如r"Newlines are indicated by /n"。

3、邏輯行與物理行

一個物理行中使用多于一個邏輯行，需要使用分號(;)來特別地標明這種用法。一個物理行只有一個邏輯行可不用分號

二、控制流

1、if

塊中不用大括號，條件后用分號，對應elif和else

if guess == number:

print 'Congratulations, you guessed it.' # New block starts here

elif guess < number:

print 'No, it is a little higher than that' # Another block

else:

print 'No, it is a little lower than that'

2、while

用分號，可搭配else

while running:

guess = int(raw_input('Enter an integer : '))

if guess == number:

print 'Congratulations, you guessed it.'

running = False # this causes the while loop to stop

elif guess < number:

print 'No, it is a little higher than that'

else:

print 'No, it is a little lower than that'

else:

print 'The while loop is over.'

# Do anything else you want to do here

3、for

用分號，搭配else

for i in range(1, 5):

print i

else:

print 'The for loop is over'

4、break和continue

同C語言

三、函數

1、定義與調用

def sayHello():

print 'Hello World!' # block belonging to the function

sayHello() # call the function

2、函數形參

類C語言

def printMax(a, b):

if a > b:

print a, 'is maximum'

else:

print b, 'is maximum'

3、局部變量

加global可申明為全局變量

4、默認參數值

def say(message, times = 1):

print message * times

5、關鍵參數

如果某個函數有許多參數，而只想指定其中的一部分，那么可以通過命名來為這些參數賦值——這被稱作關鍵參數 ——使用名字(關鍵字)而不是位置來給函數指定實參。這樣做有兩個優勢 ——一，由于不必擔心參數的順序，使用函數變得更加簡單了。二、假設其他參數都有默認值，可以只給我們想要的那些參數賦值。

def func(a, b=5, c=10):

print 'a is', a, 'and b is', b, 'and c is', c

func(3, 7)

func(25, c=24)

func(c=50, a=100)

6、return

四、模塊

1、使用模塊

import sys

print 'The command line arguments are:'

for i in sys.argv:

print i

如果想要直接輸入argv變量到程序中(避免在每次使用它時打sys.)，可以使用from sys import argv語句

2、dir()函數

可以使用內建的dir函數來列出模塊定義的標識符。標識符有函數、類和變量。

五、數據結構

1、列表

shoplist = ['apple', 'mango', 'carrot', 'banana']

print 'I have', len(shoplist),'items to purchase.'

print 'These items are:', # Notice the comma at end of the line

for item in shoplist:

print item,

print '/nI also have to buy rice.'

shoplist.append('rice')

print 'My shopping list is now', shoplist

print 'I will sort my list now'

shoplist.sort()

print 'Sorted shopping list is', shoplist

print 'The first item I will buy is', shoplist[0]

olditem = shoplist[0]

del shoplist[0]

print 'I bought the', olditem

print 'My shopping list is now', shoplist

2、元組

元組和列表十分類似，只不過元組和字符串一樣是不可變的即你不能修改元組。

zoo = ('wolf', 'elephant', 'penguin')

print 'Number of animals in the zoo is', len(zoo)

new_zoo = ('monkey', 'dolphin', zoo)

print 'Number of animals in the new zoo is', len(new_zoo)

print 'All animals in new zoo are', new_zoo

print 'Animals brought from old zoo are', new_zoo[2]

print 'Last animal brought from old zoo is', new_zoo[2][2]

像一棵樹

元組與打印

age = 22

name = 'Swaroop'

print '%s is %d years old' % (name, age)

print 'Why is %s playing with that python?' % name

3、字典

類似哈希

ab = { 'Swaroop' : 'swaroopch@byteofpython.info',

'Larry' : 'larry@wall.org',

'Matsumoto' : 'matz@ruby-lang.org',

'Spammer' : 'spammer@hotmail.com'

}

print "Swaroop's address is %s" % ab['Swaroop']

# Adding a key/value pair

ab['Guido'] = 'guido@python.org'

# Deleting a key/value pair

del ab['Spammer']

print '/nThere are %d contacts in the address-book/n' % len(ab)

for name, address in ab.items():

print 'Contact %s at %s' % (name, address)

if 'Guido' in ab: # OR ab.has_key('Guido')

print "/nGuido's address is %s" % ab['Guido']

4、序列

列表、元組和字符串都是序列。序列的兩個主要特點是索引操作符和切片操作符。

shoplist = ['apple', 'mango', 'carrot', 'banana']

# Indexing or 'Subscription' operation

print 'Item 0 is', shoplist[0]

print 'Item 1 is', shoplist[1]

print 'Item -1 is', shoplist[-1]

print 'Item -2 is', shoplist[-2]

# Slicing on a list

print 'Item 1 to 3 is', shoplist[1:3]

print 'Item 2 to end is', shoplist[2:]

print 'Item 1 to -1 is', shoplist[1:-1]

print 'Item start to end is', shoplist[:]

# Slicing on a string

name = 'swaroop'

print 'characters 1 to 3 is', name[1:3]

print 'characters 2 to end is', name[2:]

print 'characters 1 to -1 is', name[1:-1]

print 'characters start to end is', name[:]

5、參考

當你創建一個對象并給它賦一個變量的時候，這個變量僅僅參考那個對象，而不是表示這個對象本身!也就是說，變量名指向你計算機中存儲那個對象的內存。這被稱作名稱到對象的綁定。

print 'Simple Assignment'

shoplist = ['apple', 'mango', 'carrot', 'banana']

mylist = shoplist # mylist is just another name pointing to the same object!

del shoplist[0]

print 'shoplist is', shoplist

print 'mylist is', mylist

# notice that both shoplist and mylist both print the same list without

# the 'apple' confirming that they point to the same object

print 'Copy by making a full slice'

mylist = shoplist[:] # make a copy by doing a full slice

del mylist[0] # remove first item

print 'shoplist is', shoplist

print 'mylist is', mylist

# notice that now the two lists are different

6、字符串

name = 'Swaroop' # This is a string object

if name.startswith('Swa'):

print 'Yes, the string starts with "Swa"'

if 'a' in name:

print 'Yes, it contains the string "a"'

if name.find('war') != -1:

print 'Yes, it contains the string "war"'

delimiter = '_*_'

mylist = ['Brazil', 'Russia', 'India', 'China']

print delimiter.join(mylist) //用delimiter來連接mylist的字符

六、面向對象的編程

1、self

Python中的self等價于C++中的self指針和Java、C#中的this參考

2、創建類

class Person:

pass # An empty block

p = Person()

print p

3、對象的方法

class Person:

def sayHi(self):

print 'Hello, how are you?'

p = Person()

p.sayHi()

4、初始化

class Person:

def __init__(self, name):

self.name = name

def sayHi(self):

print 'Hello, my name is', self.name

p = Person('Swaroop')

p.sayHi()

5、類與對象的方法

類的變量由一個類的所有對象(實例)共享使用。只有一個類變量的拷貝，所以當某個對象對類的變量做了改動的時候，這個改動會反映到所有其他的實例上。

對象的變量由類的每個對象/實例擁有。因此每個對象有自己對這個域的一份拷貝，即它們不是共享的，在同一個類的不同實例中，雖然對象的變量有相同的名稱，但是是互不相關的。

class Person:

'''Represents a person.'''

population = 0

def __init__(self, name):

'''Initializes the person's data.'''

self.name = name

print '(Initializing %s)' % self.name

# When this person is created, he/she

# adds to the population

Person.population += 1

population屬于Person類，因此是一個類的變量。name變量屬于對象(它使用self賦值)因此是對象的變量。

6、繼承

class SchoolMember:

'''Represents any school member.'''

def __init__(self, name, age):

self.name = name

class Teacher(SchoolMember):

'''Represents a teacher.'''

def __init__(self, name, age, salary):

SchoolMember.__init__(self, name, age)

self.salary = salary

七、輸入輸出

1、文件

f = file('poem.txt', 'w') # open for 'w'riting

f.write(poem) # write text to file

f.close() # close the file

f = file('poem.txt')

# if no mode is specified, 'r'ead mode is assumed by default

while True:

line = f.readline()

if len(line) == 0: # Zero length indicates EOF

break

print line,

# Notice comma to avoid automatic newline added by Python

f.close() # close the file

2、存儲器

持久性

import cPickle as p

#import pickle as p

shoplistfile = 'shoplist.data'

# the name of the file where we will store the object

shoplist = ['apple', 'mango', 'carrot']

# Write to the file

f = file(shoplistfile, 'w')

p.dump(shoplist, f) # dump the object to a file

f.close()

del shoplist # remove the shoplist

# Read back from the storage

f = file(shoplistfile)

storedlist = p.load(f)

print storedlist

3、控制臺輸入

輸入字符串 nID = raw_input("Input your id plz")

輸入整數 nAge = int(raw_input("input your age plz:/n"))

輸入浮點型 fWeight = float(raw_input("input your weight/n"))

輸入16進制數據 nHex = int(raw_input('input hex value(like 0x20):/n'),16)

輸入8進制數據 nOct = int(raw_input('input oct value(like 020):/n'),8)

八、異常

1、try..except

import sys

try:

s = raw_input('Enter something --> ')

except EOFError:

print '/nWhy did you do an EOF on me?'

sys.exit() # exit the program

except:

print '/nSome error/exception occurred.'

# here, we are not exiting the program

print 'Done'

2、引發異常

使用raise語句引發異常。你還得指明錯誤/異常的名稱和伴隨異常觸發的異常對象。你可以引發的錯誤或異常應該分別是一個Error或Exception類的直接或間接導出類。

class ShortInputException(Exception):

'''A user-defined exception class.'''

def __init__(self, length, atleast):

Exception.__init__(self)

self.length = length

self.atleast = atleast

raise ShortInputException(len(s), 3)

3、try..finnally

import time

try:

f = file('poem.txt')

while True: # our usual file-reading idiom

line = f.readline()

if len(line) == 0:

break

time.sleep(2)

print line,

finally:

f.close()

print 'Cleaning up...closed the file'