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python集合例题_python练习题集合-2

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author：headsen chen

date：2018-06-01?15:39:26

習(xí)題17，文件的更多操作

[root@localhost py]# echo 1234567890 >cc.txt

[root@localhost py]# cat file3.py

#!/usr/bin/env pythonfromsys import argvfromos.path import exists

script,from_file,to_file=argv

print"Copying from %s to %s" %(from_file,to_file)

# we coulddo these two on one line too,how?input=open(from_file)

indata=input.read()

print"The input file is %d bytes long"%len(indata)

print"Does the output file exist? %r"%exists(to_file)

print"Ready,hit RETURN to continue, CTRL-C to abort."raw_input()

output= open(to_file,'w')

output.write(indata)

print"Alright,all done."output.close()

input.close()

[root@localhost py]#python file3.py cc.txt dd.txt

Copying fromcc.txt to dd.txt

The input fileis 11bytes long

Does the output file exist? True

Ready,hit RETURN tocontinue, CTRL-C to abort.

Alright,all done.

檢驗(yàn)新生成的dd.txt文件：

[root@localhost py]# cat dd.txt

1234567890

這里不過dd.txt是否存在，若存在：清空然后復(fù)制cc.txt的內(nèi)容過來，若不存在dd.txt文件就創(chuàng)建dd.txt文件并復(fù)制內(nèi)容過來

補(bǔ)充：exists這個(gè)命令將文件名字符串作為參數(shù)，如果文件存在的話，它將返回 True，否則將返回 False。

習(xí)題18：函數(shù) ---> 理解成“迷你腳本”

函數(shù)可以做三樣事情：

1.它們給代碼片段命名，就跟“變量”給字符串和數(shù)字命名一樣。

2.它們可以接受參數(shù)，就跟你的腳本接受 argv 一樣。

3.通過使用 #1 和 #2，它們可以讓你創(chuàng)建“微型腳本”或者“小命令”。

[root@localhost py]#cat func1.py#!/usr/bin/env python

#this is like you scripts with argv

def print_two(*args):

arg1,arg2=argsprint "arg1:%r,arg2:%r" %(arg1,arg2)#ok,that *args is actually pointless,we can just do this

defprint_two_again(arg1,arg2):print "arg1:%r,arg2:%r" %(arg1,arg2)#this just takes one argument

defprint_one(arg1):print "arg1:%r"%arg1#this one takes no arguments

defprint_none():print "I got nothing."print_two('zen','hello')

print_two_again('ZEN','HELLO')

print_one('First!')

print_none()

[root@localhost py]#python func1.py

arg1:'zen',arg2:'hello'arg1:'ZEN',arg2:'HELLO'arg1:'First!'I got nothing.

習(xí)題 19: 函數(shù)和變量

[root@localhost py]#cat func2.py#!/usr/bin/env python

defcheese_and_crackers(cheese_count, boxes_of_crackers):print "You have %d cheeses!" %cheese_countprint "You have %d boxes of crackers!" %boxes_of_crackersprint "Man that's enough for a party!"

print "Get a blanket.\n"

print "We can just give the function numbers directly:"cheese_and_crackers(20, 30)print "OR, we can use variables from our script:"amount_of_cheese= 10amount_of_crackers= 50cheese_and_crackers(amount_of_cheese, amount_of_crackers)print "We can even do math inside too:"cheese_and_crackers(10 + 20, 5 + 6)print "And we can combine the two, variables and math:"cheese_and_crackers(amount_of_cheese+ 100, amount_of_crackers + 1000)

[root@localhost py]#python func2.py

We can just give the function numbers directly:

You have20cheeses!

You have30boxes of crackers!

Man that's enough for a party!

Get a blanket.

OR, we can use variablesfromour script:

You have10cheeses!

You have50boxes of crackers!

Man that's enough for a party!

Get a blanket.

We can even do math inside too:

You have30cheeses!

You have11boxes of crackers!

Man that's enough for a party!

Get a blanket.

And we can combine the two, variablesandmath:

You have110cheeses!

You have1050boxes of crackers!

Man that's enough for a party!

Get a blanket.

習(xí)題 20: 函數(shù)和文件

[root@localhost py]#cat aa.txt

aaaaaa

bbbbbb

cccccc

[root@localhost py]#cat func-file.py

#!/usr/bin/env python

from sys importargv

script, input_file=argvdefprint_all(f):printf.read()defrewind(f):

f.seek(0)defprint_a_line(line_count, f):printline_count, f.readline()

current_file=open(input_file)print "First let's print the whole file:\n"print_all(current_file)print "Now let's rewind, kind of like a tape."rewind(current_file)print "Let's print three lines:"current_line= 1print_a_line(current_line, current_file)

current_line= current_line + 1print_a_line(current_line, current_file)

[root@localhost py]#python func-file.py aa.txt

First let's print the whole file:

aaaaaa

bbbbbb

cccccc

Now let's rewind, kind of like a tape.

Let's print three lines:

1aaaaaa2bbbbbb3 cccccc

習(xí)題 21: 函數(shù)可以返回東西

[root@localhost py]#cat func-return.py#!/usr/bin/env python#-*- coding:utf-8 -*-

defadd(a, b):print "ADDING %d + %d" %(a, b)return a +bdefsubtract(a, b):print "SUBTRACTING %d - %d" %(a, b)return a -bdefmultiply(a, b):print "MULTIPLYING %d * %d" %(a, b)return a *bdefdivide(a, b):print "DIVIDING %d / %d" %(a, b)return a /bprint "Let's do some math with just functions!"age= add(30, 5)

height= subtract(78, 4)

weight= multiply(90, 2)

iq= divide(100, 2)print "Age: %d, Height: %d, Weight: %d, IQ: %d" %(age, height,weight, iq)#A puzzle for the extra credit, type it in anyway.# pullzle:智力題

print "Here is a puzzle."what= add(age, subtract(height, multiply(weight, divide(iq,2))))print "That becomes:", what, "Can you do it by hand?"

[root@localhost py]#python func-return.py

Let's do some math with just functions!

ADDING 30 + 5SUBTRACTING78 - 4MULTIPLYING90 * 2DIVIDING100 / 2Age:35, Height: 74, Weight: 180, IQ: 50Hereisa puzzle.

DIVIDING50 / 2MULTIPLYING180 * 25SUBTRACTING74 - 4500ADDING35 + -4426That becomes:-4391 Can you do it by hand?

習(xí)題 24: 練習(xí)

[root@localhost py]#cat practise.py#!/usr/bin/env python

print "Let's practice everything."

print 'You\'d need to know \'bout escapes with \\ that do \nnewlines and \t tabs.'poem= """\tThe lovely world

with logic so firmly planted

cannot discern \n the needs of love

nor comprehend passion from intuition

and requires an explanation

\n\t\twhere there is none."""

print "--------------"

printpoemprint "--------------"five= 10 - 2 + 3 - 6

print "This should be five: %s" %fivedefsecret_formula(started):

jelly_beans= started * 500jars= jelly_beans / 1000crates= jars / 100

returnjelly_beans, jars, crates

start_point= 10000beans, jars, crates=secret_formula(start_point)print "With a starting point of: %d" %start_pointprint "We'd have %d beans, %d jars, and %d crates." %(beans,jars, crates)

start_point= start_point / 10

print "We can also do that this way:"

print "We'd have %d beans, %d jars, and %d crates." %secret_formula(start_point)

[root@localhost py]#python practise.py

Let's practice everything.

You'd need to know'bout escapes with \ that do

newlinesandtabs.--------------The lovely world

with logic so firmly planted

cannot discern

the needs of love

nor comprehend passionfromintuitionandrequires an explanation

where thereisnone.--------------This should be five:5With a starting point of:10000We'd have 5000000 beans, 5000 jars, and 50 crates.

We can also do that this way:

We'd have 500000 beans, 500 jars, and 5 crates.

習(xí)題 25: 更多的練習(xí)

[root@localhost py]#cat practise2.py#!/usr/bin/env python

defbreak_words(stuff):"""This function will break up words for us."""words= stuff.split('')returnwordsdefsort_words(words):"""Sorts the words."""

returnsorted(words)defprint_first_word(words):"""Prints the first word after popping it off."""word=words.pop(0)printworddefprint_last_word(words):"""Prints the last word after popping it off."""word= words.pop(-1)printworddefsort_sentence(sentence):"""Takes in a full sentence and returns the sorted words."""words=break_words(sentence)returnsort_words(words)defprint_first_and_last(sentence):"""Prints the first and last words of the sentence."""words=break_words(sentence)

print_first_word(words)

print_last_word(words)defprint_first_and_last_sorted(sentence):"""Sorts the words then prints the first and last one."""words=sort_sentence(sentence)

print_first_word(words)

print_last_word(words)

習(xí)題26：邏輯術(shù)語

在 python 中我們會(huì)用到下面的術(shù)語(字符或者詞匯)來定義事物的真(True)或者假(False)。計(jì)算機(jī)的邏輯就是在程序的某個(gè)位置檢查這些字符或者變量組合

在一起表達(dá)的結(jié)果是真是假。

? and 與

? or 或

? not 非

? != (not equal) 不等于

? == (equal) 等于

? >= (greater-than-equal) 大于等于

? <= (less-than-equal) 小于等于

? True 真

? False 假

真值表

我們將使用這些字符來創(chuàng)建你需要記住的真值表。

not False True

not True False

True or FalseTrue

True or True True

False or True True

False or False False

True and FalseFalse

True and True True

False and True False

False and False False

not (True or False) False

not (True or True) False

not (False or True) False

not (False or False) True

not (True and False) True

not (True and True) False

not (False and True) True

not (False and False) True

1 != 0 True

1 != 1 False

0 != 1 True

0 != 0 False

1 == 0 False

1 == 1 True

0 == 1 False

0 == 0 True

習(xí)題27：bool 值運(yùn)算

[root@localhost py]# cat bool.py

#!/usr/bin/env python

print True and True

print False and True

print 1 == 1 and 2 == 1

print "test" == "test"

print 1 == 1 or 2 != 1

print True and 1 == 1

print False and 0 != 0

print True or 1 == 1

print "test" == "testing"

print 1 != 0 and 2 == 1

print "test" != "testing"

print "test" == 1

print not (True and False)

print not (1 == 1 and 0 != 1)

print not (10 == 1 or 1000 == 1000)

print not (1 != 10 or 3 == 4)

print not ("testing" == "testing" and "Zed" == "Cool Guy")

print 1 == 1 and not ("testing" == 1 or 1 == 0)

print "chunky" == "bacon" and not (3 == 4 or 3 == 3)

print 3 == 3 and not ("testing" == "testing" or "Python" == "Fun")

[root@localhost py]# python bool.py

True

False

True

False

True

False

True

False

True

False

True

False

習(xí)題28：bool運(yùn)算

3 != 4 and not ("testing" != "test" or "Python" == "Python")

接下來你將看到這個(gè)復(fù)雜表達(dá)式是如何逐級(jí)解為一個(gè)單獨(dú)結(jié)果的：1. 解出每一個(gè)等值判斷:

a.3 != 4 為 True : True and not ("testing" != "test" or "P

ython"=="Python")

b. "testing" != "test" 為 True : True and not (True or "Pyt

hon"=="Python")

c. "Python" == "Python" : True and not (True orTrue)2. 找到括號(hào)中的每一個(gè) and/or:

a. (Trueor True) 為 True: True and not(True)3. 找到每一個(gè) not并將其逆轉(zhuǎn):

a.not (True) 為 False: True andFalse4. 找到剩下的 and/or，解出它們的值:

a. TrueandFalse 為 False

這樣我們就解出了它最終的值為 False.

View Code

習(xí)題 29: 如果(if)

[root@localhost py]#cat if.py#!/usr/bin/env python

people = 20cats= 30dogs= 15

if people

if people >cats:print "Not many cats! The world is saved!"

if people

if people >dogs:print "The world is dry!"dogs+= 5

if people >=dogs:print "People are greater than or equal to dogs."

if people <=dogs:print "People are less than or equal to dogs."

if people ==dogs:print "People are dogs."

View Code

[root@localhost py]#python if.py

Too many cats! The world isdoomed!

The worldisdry!

People are greater thanorequal to dogs.

People are less thanorequal to dogs.

People are dogs.

View Code

習(xí)題30：if -elase 結(jié)合使用

[root@localhost py]#cat if.py#!/usr/bin/env python

people = 20cats= 30dogs= 15

if people

if people >cats:print "Not many cats! The world is saved!"

if people

if people >dogs:print "The world is dry!"dogs+= 5

if people >=dogs:print "People are greater than or equal to dogs."

if people <=dogs:print "People are less than or equal to dogs."

if people ==dogs:print "People are dogs."

View Code

[root@localhost py]# python if-else.py

We should take the cars.

Maybe we could take the buses.

Alright, let's just take the buses.

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