python代码运行时显示else(38行）语法错误，这是copy的代码，但不知道为什么还是运行不了，求解答。

dashes = '\n' + '-'*50
exec_dict ={

'f':"""
for %s in %s
print %s
""",

's':"""
%s=0
%s=%s
while %s < len(%s)
print %s[%s]
%s=%s+1
""",

'n':"""
%s=%d
while %s < %d
print %s
%s=%s+%d
"""
}

def main():

ltype = raw_input('Loop type?(For/While)')
dtype = raw_input('Data type?(Number/seq)')

if dtype =='n':
    start = input('Starting value?')
    stop = input('Ending value (non-inclusive)?')
    step = input('Stepping value?')
    seq = str(range(start,stop,step))

else:
seq = raw_input('Enter sequence:')

var = raw_input('Iterative variable name?')

if ltype =='f'
    exec_str = exec_dict['f'] % (var,seq,var)

elif ltype =='w':
    if dtype =='s':
        svar = raw_input('Enter sequence name?')
        exec_str =exec_dict['s'] % \
(var,svar,seq,var,svar,svar,var,var,var)

    elif dtype =='n':
        exec_str = exec_dict['n'] % \
(var,start,var,stop,var,var,var,step)

print dashes
print'Your custom-generated code:' + dashes
print exec_str + dashes
print 'Test execution of the code:' + dashes
exec exec_str
print dashes

if_name_ =='main':
main()

---

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

dashes = '\n' + '-'*50
exec_dict ={

'f':"""
for %s in %s
print %s
""",

's':"""
%s=0
%s=%s
while %s < len(%s)
print %s[%s]
%s=%s+1
""",

'n':"""
%s=%d
while %s < %d
print %s
%s=%s+%d
"""
}

def main():

    ltype = raw_input('Loop type?(For/While)')
    dtype = raw_input('Data type?(Number/seq)')

    if dtype =='n':
        start = input('Starting value?')
        stop = input('Ending value (non-inclusive)?')
        step = input('Stepping value?')
        seq = str(range(start,stop,step))
    else:
        seq = raw_input('Enter sequence:')

        var = raw_input('Iterative variable name?')

    if ltype =='f':
        exec_str = exec_dict['f'] % (var,seq,var)

    elif ltype =='w':
        if dtype =='s':
            svar = raw_input('Enter sequence name?')
            exec_str =exec_dict['s'] % \
    (var,svar,seq,var,svar,svar,var,var,var)

        elif dtype =='n':
            exec_str = exec_dict['n'] % \
    (var,start,var,stop,var,var,var,step)

    print dashes
    print'Your custom-generated code:' + dashes
    print exec_str + dashes
    print 'Test execution of the code:' + dashes
    exec exec_str
    print dashes
if __name__ =='main':
    main()