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从python生成器打印所有结果

generator python-3.x python

Jacob Fuchs · 技术社区 · 7 年前

我做了一个生成器函数,它使用关键字搜索csv文件,如果有什么结果,我想打印出来。我怎样才能在不反复使用打印(下一代(gen_results))的情况下做到这一点?

我尝试了一个stopIteration的try-catch语句,当关键字与联系人不匹配时,我希望有一个更简洁的解决方案。

def search(keyword, filename):
    f = open(filename, 'r')
    for line in f:
        if keyword in line:
            yield line
    f.close()

the_generator = search('Python', 'contacts.csv')
print(next(the_generator))
print(next(the_generator))  

contacts.csv
Name01, 89888
Name02, 8885445
Name03, 54555
Name04, 55544584
Name05, 55855
Python, 100
BigPi, 444
Python, 101

如果关键字没有联系人,我希望输出是一个“NothingFound”语句。如果有带有关键字的联系人,它将输出所有列表。

4 回复 | 直到 7 年前

Patrick Artner 7 年前

有几种方法可以消耗发电机运行 next() 只消耗它的(下一个)值。

生成文件:

def gen_file():
    with open("contacts.csv","w") as f:
        f.write("""Name01, 89888
Name02, 8885445
Name03, 54555
Name04, 55544584
Name05, 55855
Python, 100
BigPi, 444
Python, 101
""")

使用它:

gen_file()   

def search(keyword, filename="contacts.csv"):
    """Changed to use .. with open() as f: ... style syntax."""
    with open(filename, 'r') as f:
        for line in f:
            if keyword in line:
                yield line 


# consume all of it into a list - you can reuse it
print("-"*40)
the_generator = search('Python', 'contacts.csv')
contacts = list(the_generator)
print(*contacts, sep="")


print("-"*40)
# decompose the generator directly for printing
the_generator = search('Python', 'contacts.csv')
print(*the_generator, sep="" ) 


print("-"*40)
# use a for loop over the generated results
the_generator = search('Python', 'contacts.csv')
for li in the_generator:
    print(li, end="") # remove end=\n


print("-"*40)
# using str.join to create the output
the_generator = search('Python', 'contacts.csv')
print("".join(the_generator))


print("-"*40)
# loop endlessly until StopIteration is raised
try:
    while True:
        print(next(the_generator), end="")
except StopIteration:
    pass

等。

输出(几次):

----------------------------------------
Python, 100
Python, 101

如果不重用生成的值,则“最佳”值可能是 print(*the_generator,sep="") 或者更明确地说:

# use a for loop over the generated results
the_generator = search('Python', 'contacts.csv')
for li in the_generator:
    print(li,end="") # remove end=\n

您也可以在这里阅读: Using yield from with conditional in python

BlueSheepToken 7 年前

请试试这个

def search(keyword, filename):
    f = open(filename, 'r')
    for line in f:
        if keyword in line:
            yield line
        else:
            yield 'Nothing Found'
    f.close()

the_generator = search('Python', 'contacts.csv')
for g in the_generator:
    print(g)

“the_generator”是一个迭代对象,“for”循环需要一个迭代对象才能运行。程序输出将:

Nothing Found
Nothing Found
Nothing Found
Nothing Found
Nothing Found
Python, 100

Bitto 7 年前

def search(keyword, filename):
    f = open(filename, 'r')
    for line in f:
        if keyword in line:
            yield line
    f.close()

the_generator = search('Python', 'contacts.csv')
my_list=list(the_generator)
if not my_list:
    print("Not Found")
for item in my_list:
    print(item.strip())

hpaulj 7 年前

您可以将“未找到”测试放入生成器本身:

def search(keyword, lines):
    cnt = 0
    for line in lines:
        if keyword in line:
            cnt += 1
            yield line
    if cnt==0:
        yield "NOT FOUND"

In [166]: txt = """Name01, 89888
     ...: Name02, 8885445
     ...: Name03, 54555
     ...: Name04, 55544584
     ...: Name05, 55855
     ...: Python, 100
     ...: BigPi, 444
     ...: Python, 101
     ...: """.splitlines()
In [167]: for x in search("Python",txt):print(x)
Python, 100
Python, 101
In [168]: for x in search("Foobar",txt):print(x)
NOT FOUND

否则我认为最简单的是 list 并检查空列表。生成器机制本身不计算 yields .