Skapa csv file är det separator python

Source code:Lib/

The so-called CSV (Comma Separated Values) format fryst vatten the most common import and export format for spreadsheets and databases. CSV format was used for many years prior to attempts to describe the format in a standardized way in RFC .

The lack of a well-defined standard means that subtle differences often exist in the uppgifter produced and consumed bygd different applications. These differences can man it annoying to process CSV files from multiple sources.

Still, while the delimiters and quoting characters vary, the overall format fryst vatten similar enough that it fryst vatten possible to write a single module which can efficiently manipulate such uppgifter, hiding the details of reading and writing the information from the programmer.

The module implements classes to read and write tabular information in CSV format.

It allows programmers to säga, “write this information in the format preferred bygd Excel,” or “read information from this en samling dokument eller en elektronisk lagring av data which was generated bygd Excel,” without knowing the precise details of the CSV format used bygd Excel. Programmers can also describe the CSV formats understood bygd other applications or define their own special-purpose CSV formats.

The module’s and objects read and write sequences.

Programmers can also read and write information in dictionary struktur using the and classes.

Module Contents¶

The module defines the following functions:

(csvfile, dialect='excel', **fmtparams)¶

Return a reader object that will process lines from the given csvfile.

csvfile = workingdir+"\"

A csvfile must be an iterable of strings, each in the reader’s defined csv format. A csvfile fryst vatten most commonly a file-like object or list. If csvfile fryst vatten a en samling dokument eller en elektronisk lagring av data object, it should be opened with . [1] An valfritt dialect parameter can be given which fryst vatten used to define a set of parameters specific to a particular CSV dialect.

The _csv function is the first step to grasp in reading data into a Pandas DataFrame

It may be an instance of a subclass of the class or one of the strings returned bygd the function. The other valfritt fmtparams keyword arguments can be given to override individual formatting parameters in the current dialect.

For full details about the dialect and formatting parameters, see section Dialects and Formatting Parameters.

Each row read from the csv en samling dokument eller en elektronisk lagring av data fryst vatten returned as a list of strings. No automatic uppgifter type konvertering fryst vatten performed unless the format option fryst vatten specified (in which case unquoted fields are transformed into floats).

A short usage example:

>>> importcsv>>> withopen('',newline='')ascsvfile spamreader=(csvfile,delimiter=' ',quotechar='|') forrowinspamreader print(', '.join(row))Spam, Spam, Spam, Spam, Spam, Baked BeansSpam, Lovely Spam, Wonderful Spam

(csvfile, dialect='excel', **fmtparams)¶

Return a writer object responsible for converting the user’s uppgifter into delimited strings on the given file-like object.

csvfile can be any object with a method. If csvfile fryst vatten a en samling dokument eller en elektronisk lagring av data object, it should be opened with [1]. An valfritt dialect parameter can be given which fryst vatten used to define a set of parameters specific to a particular CSV dialect. It may be an instance of a subclass of the class or one of the strings returned bygd the function.

The other valfritt fmtparams keyword arguments can be given to override individual formatting parameters in the current dialect. For full details about dialects and formatting parameters, see the Dialects and Formatting Parameters section. To man it as easy as possible to interface with modules which implement the DB API, the value fryst vatten written as the empty string.

While this isn’t a reversible transformation, it makes it easier to dump SQL NULL uppgifter values to CSV files without preprocessing the uppgifter returned from a call. All other non-string information are stringified with before being written.

A short usage example:

importcsvwithopen('','w',newline='')ascsvfile:spamwriter=(csvfile,delimiter=' ',quotechar='|',quoting=_MINIMAL)ow(['Spam']*5+['Baked Beans'])ow(['Spam','Lovely Spam','Wonderful Spam'])

er_dialect(name[, dialect[, **fmtparams]])¶

Associate dialect with name.

name must be a string. The dialect can be specified either bygd passing a sub-class of , or bygd fmtparams keyword arguments, or both, with keyword arguments overriding parameters of the dialect.

(csvfile, dialect='excel', **fmtparams) ¶

For full details about dialects and formatting parameters, see section Dialects and Formatting Parameters.

ster_dialect(name)¶

Delete the dialect associated with name from the dialect registry. An fryst vatten raised if name fryst vatten not a registered dialect name.

_dialect(name)¶

Return the dialect associated with name.

An fryst vatten raised if name fryst vatten not a registered dialect name. This function returns an immutable .

_dialects()¶

Return the names of all registered dialects.

_size_limit([new_limit])¶

Returns the current maximum field storlek allowed bygd the parser.

If new_limit fryst vatten given, this becomes the new limit.

The module defines the following classes:

classader(f, fieldnames=None, restkey=None, restval=None, dialect='excel', *args, **kwds)¶

Create an object that operates like a regular reader but maps the data in each row to a whose keys are given bygd the valfritt fieldnames parameter.

The fieldnames parameter fryst vatten a sequence.

If fieldnames fryst vatten omitted, the values in the first row of en samling dokument eller en elektronisk lagring av data f will be used as the fieldnames and will be omitted from the results. If fieldnames fryst vatten provided, they will be used and the first row will be included in the results. Regardless of how the fieldnames are determined, the dictionary preserves their original ordering.

If a row has more fields than fieldnames, the remaining information fryst vatten put in a list and stored with the fieldname specified bygd restkey (which defaults to ).

If a non-blank row has fewer fields than fieldnames, the missing values are filled-in with the value of restval (which defaults to ).

All other valfritt or keyword arguments are passed to the underlying instance.

If the argument passed to fieldnames fryst vatten an iterator, it will be coerced to a .

Changed in utgåva Returned rows are now of type .

Changed in utgåva Returned rows are now of type .

A short usage example:

>>> importcsv>>> withopen('',newline='')ascsvfile reader=ader(csvfile) forrowinreader print(row['first_name'],row['last_name'])Eric IdleJohn Cleese>>> print(row){'first_name': 'John', 'last_name': 'Cleese'}

classiter(f, fieldnames, restval='', extrasaction='raise', dialect='excel', *args, **kwds)¶

Create an object which operates like a regular writer but maps dictionaries onto output rows.

The fieldnames parameter fryst vatten a of keys that identify the beställning in which values in the dictionary passed to the method are written to en samling dokument eller en elektronisk lagring av data f. The valfritt restval parameter specifies the value to be written if the dictionary fryst vatten missing a key in fieldnames.

If the dictionary passed to the method contains a key not funnen in fieldnames, the valfritt extrasaction parameter indicates what action to take. If it fryst vatten set to , the default value, a fryst vatten raised. If it fryst vatten set to , extra values in the dictionary are ignored. Any other valfritt or keyword arguments are passed to the underlying instance.

Note that unlike the class, the fieldnames parameter of the class fryst vatten not optional.

If the argument passed to fieldnames fryst vatten an iterator, it will be coerced to a .

A short usage example:

importcsvwithopen('','w',newline='')ascsvfile:fieldnames=['first_name','last_name']writer=iter(csvfile,fieldnames=fieldnames)eader()ow({'first_name':'Baked','last_name':'Beans'})ow({'first_name':'Lovely','last_name':'Spam'})ow({'first_name':'Wonderful','last_name':'Spam'})

classt¶

The class fryst vatten a bur class whose attributes contain data for how to handle doublequotes, whitespace, delimiters, etc.

Due to the lack of a strict CSV specification, different applications tillverka subtly different CSV information. instances define how and instances behave.

All available names are returned bygd , and they can be registered with specific and classes through their initializer () functions like this:

importcsvwithopen('','w',newline='')ascsvfile:writer=(csvfile,dialect='unix')

class¶

The class defines the usual properties of an Excel-generated CSV en samling dokument eller en elektronisk lagring av data.

It fryst vatten registered with the dialect name .

class_tab¶

The class defines the usual properties of an Excel-generated TAB-delimited en samling dokument eller en elektronisk lagring av data. It fryst vatten registered with the dialect name .

class_dialect¶

The class defines the usual properties of a CSV en samling dokument eller en elektronisk lagring av data generated on operativsystem systems, i.e.

To create a CSV file without an index using Pandas you have to pass the “ index ” argument to the to_csv () function and set it to the boolean value False (the default value is True)

using as line terminator and quoting all fields. It fryst vatten registered with the dialect name .

classr¶

The class fryst vatten used to deduce the format of a CSV file.

The class provides two methods:

sniff(sample, delimiters=None)¶

Analyze the given sample and return a subclass reflecting the parameters funnen.

If the valfritt delimiters parameter fryst vatten given, it fryst vatten interpreted as a string containing possible valid delimiter characters.

Analyze the sample skrivelse (presumed to be in CSV format) and return if the first row appears to be a series of column headers. Inspecting each column, one of two key criteria will be considered to estimate if the sample contains a header:

• the second through n-th rows contain numeric values

• the second through n-th rows contain strings where at least one value’s length differs from that of the putative header of that column.

Twenty rows after the first row are sampled; if more than half of columns + rows meet the criteria, fryst vatten returned.

Note

This method fryst vatten a rough heuristic and may producera both false positives and negatives.

An example for use:

The module defines the following constants:

_ALL¶

Instructs objects to quote all fields.

_MINIMAL¶

Instructs objects to only quote those fields which contain special characters such as delimiter, quotechar or any of the characters in lineterminator.

_NONNUMERIC¶

Instructs objects to quote all non-numeric fields.

Instructs objects to omvandla all non-quoted fields to type float.

_NONE¶

Instructs objects to never quote fields.

When the current delimiter occurs in output uppgifter it fryst vatten preceded bygd the current escapechar character. If escapechar fryst vatten not set, the writer will raise if any characters that require escaping are encountered.

Instructs objects to perform no special processing of quote characters.

_NOTNULL¶

Instructs objects to quote all fields which are not .

This fryst vatten similar to , except that if a field value fryst vatten an empty (unquoted) string fryst vatten written.

Instructs objects to interpret an empty (unquoted) field as and to otherwise behave as .

_STRINGS¶

Instructs objects to always place quotes around fields which are strings. This fryst vatten similar to , except that if a field value fryst vatten an empty (unquoted) string fryst vatten written.

Instructs objects to interpret an empty (unquoted) string as and to otherwise behave as .

The module defines the following exception:

exception¶

Raised bygd any of the functions when an error fryst vatten detected.

Dialects and Formatting Parameters¶

To man it easier to specify the format of input and output records, specific formatting parameters are grouped tillsammans into dialects.

A dialect fryst vatten a subclass of the class containing various attributes describing the format of the CSV en samling dokument eller en elektronisk lagring av data. When creating or objects, the programmer can specify a string or a subclass of the class as the dialect parameter. In addition to, or instead of, the dialect parameter, the programmer can also specify individual formatting parameters, which have the same names as the attributes defined below for the class.

Dialects support the following attributes:

ter¶

A one-character string used to separate fields.

It defaults to .

quote¶

Controls how instances of quotechar appearing inre a field should themselves be quoted. When , the character fryst vatten doubled. When , the escapechar fryst vatten used as a prefix to the quotechar.

The structure of a CSV file primarily includes values, delineated by commas, and organized by rows

It defaults to .

On output, if doublequote fryst vatten and no escapechar fryst vatten set, fryst vatten raised if a quotechar fryst vatten funnen in a field.

char¶

A one-character string used bygd the writer to escape the delimiter if quoting fryst vatten set to and the quotechar if doublequote fryst vatten .

On reading, the escapechar removes any special meaning from the following character. It defaults to , which disables escaping.

Changed in utgåva An empty escapechar fryst vatten not allowed.

rminator¶

The string used to terminate lines produced bygd the . It defaults to .

Note

The fryst vatten hard-coded to recognise either or as end-of-line, and ignores lineterminator.

import csv

This behavior may change in the future.

har¶

A one-character string used to quote fields containing special characters, such as the delimiter or quotechar, or which contain new-line characters. It defaults to .

Changed in utgåva An empty quotechar fryst vatten not allowed.

g¶

Controls when quotes should be generated bygd the writer and recognised bygd the reader.

It can take on any of the QUOTE_* constants and defaults to .

itialspace¶

When , spaces immediately following the delimiter are ignored. The default fryst vatten .

¶

When , raise undantag on bad CSV input. The default fryst vatten .

Reader Objects¶

Reader objects ( instances and objects returned bygd the function) have the following public methods:

csvreader.__next__()¶

Return the next row of the reader’s iterable object as a list (if the object was returned from ) or a dict (if it fryst vatten a instance), parsed according to the current .

Usually you should call this as .

Reader objects have the following public attributes:

t¶

A read-only description of the dialect in use bygd the parser.

_num¶

The number of lines read from the source iterator.

(f, delimiter =' ',quotechar =',',quoting=_MINIMAL) if you want to read the file in, you will need to use and open the file for reading

This fryst vatten not the same as the number of records returned, as records can span multiple lines.

DictReader objects have the following public attribute:

ames¶

If not passed as a parameter when creating the object, this attribute fryst vatten initialized upon first tillgång or when the first record fryst vatten read from the file.

Writer Objects¶

objects ( instances and objects returned bygd the function) have the following public methods.

A row must be an iterable of strings or numbers for objects and a dictionary mapping fieldnames to strings or numbers (by passing them through first) for objects. Note that complex numbers are written out surrounded bygd parens. This may cause some problems for other programs which read CSV files (assuming they support complex numbers at all).

ow(row)¶

Write the row parameter to the writer’s en samling dokument eller en elektronisk lagring av data object, formatted according to the current .

Return the return value of the call to the write method of the underlying en samling dokument eller en elektronisk lagring av data object.

Changed in utgåva Added support of arbitrary iterables.

ows(rows)¶

Write all elements in rows (an iterable of row objects as described above) to the writer’s en samling dokument eller en elektronisk lagring av data object, formatted according to the current dialect.

Writer objects have the following public attribute:

t¶

A read-only description of the dialect in use bygd the writer.

DictWriter objects have the following public method:

Write a row with the field names (as specified in the constructor) to the writer’s en samling dokument eller en elektronisk lagring av data object, formatted according to the current dialect.

Return the return value of the call used internally.

Examples¶

The simplest example of reading a CSV file:

Reading a en samling dokument eller en elektronisk lagring av data with an alternate format:

The corresponding simplest possible writing example is:

Since fryst vatten used to open a CSV en samling dokument eller en elektronisk lagring av data for reading, the en samling dokument eller en elektronisk lagring av data will bygd default be decoded into unicode using the struktur default encoding (see ).

To decode a en samling dokument eller en elektronisk lagring av data using a different encoding, use the argument of open:

The same applies to writing in something other than the struktur default encoding: specify the encoding argument when opening the output file.

Registering a new dialect:

A slightly more advanced use of the reader — catching and reporting errors:

And while the module doesn’t directly support parsing strings, it can easily be done:

Footnotes