从第2行读取文件或跳过标题行

如何跳过标题行并开始从第2行读取文件？

with open(fname) as f:
    next(f)
    for line in f:
        #do something

f = open(fname,'r')
lines = f.readlines()[1:]
f.close()

如果要第一行，然后要对文件执行一些操作，此代码将很有帮助。

with open(filename , 'r') as f:
    first_line = f.readline()
    for line in f:
            # Perform some operations

如果切片可以在迭代器上工作...

from itertools import islice
with open(fname) as f:
    for line in islice(f, 1, None):
        pass

f = open(fname).readlines()
firstLine = f.pop(0) #removes the first line
for line in f:
    ...

为了概括读取多个标题行的任务并提高可读性，我将使用方法提取。假设您想标记化前三行coordinates.txt以用作标题信息。

例

coordinates.txt
---------------
Name,Longitude,Latitude,Elevation, Comments
String, Decimal Deg., Decimal Deg., Meters, String
Euler's Town,7.58857,47.559537,0, "Blah"
Faneuil Hall,-71.054773,42.360217,0
Yellowstone National Park,-110.588455,44.427963,0

然后提取方法允许你指定什么，你想用头信息做（在这个例子中，我们简单的记号化基础上，逗号标题行并返回一个列表，但有足够的空间做更多的工作）。

def __readheader(filehandle, numberheaderlines=1):
    """Reads the specified number of lines and returns the comma-delimited 
    strings on each line as a list"""
    for _ in range(numberheaderlines):
        yield map(str.strip, filehandle.readline().strip().split(','))

with open('coordinates.txt', 'r') as rh:
    # Single header line
    #print next(__readheader(rh))

    # Multiple header lines
    for headerline in __readheader(rh, numberheaderlines=2):
        print headerline  # Or do other stuff with headerline tokens

输出量

['Name', 'Longitude', 'Latitude', 'Elevation', 'Comments']
['String', 'Decimal Deg.', 'Decimal Deg.', 'Meters', 'String']

如果coordinates.txt包含另一个标题行，只需更改numberheaderlines。最重要的是，很清楚__readheader(rh, numberheaderlines=2)正在做什么，并且我们避免了必须弄清楚或评论为什么接受的答案的作者next()在其代码中使用原因的含糊之处。

如果您想从第2行开始读取多个CSV文件，这就像一个超级按钮

for files in csv_file_list:
        with open(files, 'r') as r: 
            next(r)                  #skip headers             
            rr = csv.reader(r)
            for row in rr:
                #do something

（这是帕菲特对另一个问题的回答的一部分）

# Open a connection to the file
with open('world_dev_ind.csv') as file:

    # Skip the column names
    file.readline()

    # Initialize an empty dictionary: counts_dict
    counts_dict = {}

    # Process only the first 1000 rows
    for j in range(0, 1000):

        # Split the current line into a list: line
        line = file.readline().split(',')

        # Get the value for the first column: first_col
        first_col = line[0]

        # If the column value is in the dict, increment its value
        if first_col in counts_dict.keys():
            counts_dict[first_col] += 1

        # Else, add to the dict and set value to 1
        else:
            counts_dict[first_col] = 1

# Print the resulting dictionary
print(counts_dict)