第二章习题

2-1

>>> a1=232
>>> a1
232
>>> print a1
232
>>> type(a1)
<type 'int'>
>>> a2='wef23'
>>> a2
'wef23'
>>> print a2
wef23
>>> type(a2)
<type 'str'>
>>> a3=[32,'322']
>>> a3
[32, '322']
>>> print a3
[32, '322']
>>> type(a3)
<type 'list'>
>>> a4=(23,'23')
>>> a4
(23, '23')
>>> print a4
(23, '23')
>>> type(a4)
<type 'tuple'>

2-2

/article/7675454.html

https://www.zhihu.com/question/20790240

两个参考链接

(a)

用python可执行程序去运行，调用/usr/bin/env 下的python来执行。为了防止用户没有将python装在默认的/usr/bin路径里，当执行时，首先到env中查找python的安装路径，再调用对应路径下的解释器程序来完成。 #!/usr/bin/python写死了python路径。

数字计算

(b)

#!/usr/bin/env python
1+2*4

没有输出

(c)

没有以变量的形式给输出或打印

(d)

有何不同？

9

(e)

#!/usr/bin/env python
print 1+2*4

2-3

>>> a=2;b=5
>>> print a+b  #jiafa
7
>>> print a-b #jianfa
-3
>>> print a*b #chengfa
10
>>> print a/b  #chufa
0
>>> print a%b #quyu
2
>>> print a//b
0
>>> print a**b  #chengfang
32

2-4

(a)

>>> raw_input("please enter a char:")
please enter a char:fa
'fa'

(b)

>>> a=raw_input("please enter a number:")
please enter a number:54
>>> a
'54'
>>> b=int(raw_input("please enter a number:"))
please enter a number:54
>>> b
54
>>> type(a)
<type 'str'>
>>> type(b)
<type 'int'>

2-5

(a)

while

>>> #!/usr/bin/env python
>>> i=0
>>> while i<11:
print i
i+=1

0
1
2
3
4
5
6
7
8
9
10

(b)

for

>>> for i in range(11):
print i

0
1
2
3
4
5
6
7
8
9
10

2-6

#!/usr/bin/env python
i = raw_input("please input a number:")
i=int(i)
if i>0:
print "%d is more than 0" % i
elif i<0:
print "%d is less than 0" % i
else:
print "%d is equal 0" % i

2-7

while

#!/usr/bin/env python
char1 = raw_input("please input a char:")
num =len(char1)
i=0
while i<num:
print char1[i]
i+=1

please input a char:juanjuan
j
u
a
n
j
u
a
n

for

#!/usr/bin/env python
char1 = raw_input("please input a char:")
num =len(char1)
for i in range(num):
print char1[i]

please input a char:juanjaun
j
u
a
n
j
a
u
n

2-8

预先输入

#!/usr/bin/env python
a=[23,32,43,54,73]
i=len(a)
j=0;sum1=0
while j<i:
sum1+=a[j]
j+=1
print  sum1

接受用户输入

#!/usr/bin/env python
a=[1,1,1,1,1]
i=len(a)
j=0;sum1=0
while j<i:
a[j]=raw_input("please input a number:")
sum1+=int(a[j])
j+=1
print  sum1

for

预先输入

#!/usr/bin/env python
a=[234,34,2,322,24]
i=len(a)
j=0;sum1=0
for  j in range(i):
#a[j]=raw_input("please input a number:")
sum1+=int(a[j])
# j+=1
print  sum1

用户输入

#!/usr/bin/env python
a=[1,2,3,4,5]
i=len(a)
j=0;sum1=0
for  j in range(i):
a[j]=raw_input("please input a number:")
sum1+=int(a[j])
print  sum1

注明：元组不支持修改

2-9

#!/usr/bin/env python
a=[23,32,43,443,5]
i=len(a)
j=0;sum1=0
for  j in range(i):
#a[j]=raw_input("please input a number:")
sum1+=int(a[j])
print  float(sum1)/float(i)

2-10

#!/usr/bin/env python
#coding:utf-8
while True:
a=int(raw_input("please input a number:"))
if a>=1 and a<=100:
print "%d is good" % (a)
break
else :
print "mistake,retry!"
continue

2-11

#!/usr/bin/env python
#coding:utf-8

def Menu():
print "================================"
print "[1]get sum from 5 numbers"
print "[2]get average from 5 numbers"
print "[X]Exit"

def Sum():
list=[1,2,3,4,5]
sum=0
for i in xrange(len(list)):
list[i]=raw_input("input a %d Number:" %(i+1))
sum+=int(list[i])
i+=1
return sum

def Aver():
sum=Sum()
return sum/5

while True:
Menu()
choice = raw_input("please choice one:")
if choice == '1':
SUM=Sum()
print "sum is :%d" % SUM
print
continue
elif choice == '2':
Average = Aver()
print "Average is:%f" % Average
continue
elif choice == 'X':
break
else:
print "wrong choose,please again!"
continue

2-12

(a)

>>> dir()
['__builtins__', '__doc__', '__name__', '__package__', 'a', 'b', 'i', 'k']

显示每个值

>>> __builtins__
<module '__builtin__' (built-in)>
>>> __doc__
>>> __name__
'__main__'
>>> __package__
>>> a
[23, 32, 43, 54, 73]
>>> b
54
>>> i
2
>>> k
'5'

(b)

(c)

(d)

2-13

(a)

>>> dir()
['__builtins__', '__doc__', '__name__', '__package__', 'a', 'b', 'i', 'k']>>> import sys
>>> dir()
['__builtins__', '__doc__', '__name__', '__package__', 'a', 'b', 'i', 'k', 'sys']
>>> dir(sys)
['__displayhook__', '__doc__', '__egginsert', '__excepthook__', '__name__', '__package__', '__plen', '__stderr__', '__stdin__', '__stdout__', '_clear_type_cache', '_current_frames', '_getframe', '_mercurial', 'api_version', 'argv', 'builtin_module_names', 'byteorder', 'call_tracing', 'callstats', 'copyright', 'displayhook', 'dllhandle', 'dont_write_bytecode', 'exc_clear', 'exc_info', 'exc_traceback', 'exc_type', 'exc_value', 'excepthook', 'exec_prefix', 'executable', 'exit', 'flags', 'float_info', 'float_repr_style', 'getcheckinterval', 'getdefaultencoding', 'getfilesystemencoding', 'getprofile', 'getrecursionlimit', 'getrefcount', 'getsizeof', 'gettrace', 'getwindowsversion', 'hexversion', 'last_traceback', 'last_type', 'last_value', 'long_info', 'maxint', 'maxsize', 'maxunicode', 'meta_path', 'modules', 'path', 'path_hooks', 'path_importer_cache', 'platform', 'prefix', 'py3kwarning', 'setcheckinterval', 'setprofile', 'setrecursionlimit', 'settrace', 'stderr', 'stdin', 'stdout', 'subversion', 'version', 'version_info', 'warnoptions', 'winver']

(b)

>>> sys.api_version
1013
>>> sys.platform
'win32'

(c)

>>> sys.exit()

2-14

>>> print -2*4+3**2
1
>>> print (-2*4)+(3**2)
1

没有错

2-15

#!/usr/bin/env python
#coding:utf-8

i=0
j=3
a=0;b=0;c=0

a=raw_input("a=")
b=raw_input("b=")
c=raw_input("c=")
if a >b:
if b>c:
print "%s>%s>%s" %(a,b,c)
elif c>b:
print "%s>%s>%s" %(a,c,b)
elif b>a:
if a>c:
print "%s>%s>%s" %(b,a,c)
elif c>a:
print "%s>%s>^%s" % (b,c,a)
elif c>b:
if b>a:
print "%s>%s>%s" %(c,b,a)
elif a>b:
print "%s>%s>%s" %( c , b ,a)
elif a == b:
if a > c:
print "%s=%s>%s" %(a,b,c)
elif a<c:
print "%s>%s=%s" %(c,a,b)
elif a == c:
if a>b:
print "%s=%s>%s" %(a,c,b)
elif b>a:
print "%s>%s=%s" %(b,a,c)
elif b == c:
if b>a:
print "%s=%s>%s" % (b,c,a)
elif a>b:
print "%s>%s=%s" %(a,b,c)
else :
print "%s=%s=%s" %(a,b,c)

2-16

#!/usr/bin/env python
filename=raw_input("Enter file name:")
fobj=open(filename,'r')
for eachLine in fobj:
print eachLine,

fobj.close()